engineering workshop lab manual

Transcription

ENGINEERING WORKSHOP
LAB MANUAL
Engineering Work Shop
Department of Mechanical Engineering
Page 2
CONTENTS
Instructions for Laboratory
S.No.
Experiment
……….4
Page no.
1.
BLACKSMITHY
6
2.
CARPENTRY
13
3.
FITTING
22
4.
FOUNDRY
31
5.
TINSMITHY
42
6.
WELDING
50
7.
HOUSEWIRING
61
8.
PUMBLING
69
9.
POWER TOOLS
74
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Instructions for Laboratory

The objective of the laboratory is learning. The experiments are designed to illustrate phenomena
in different areas of Workshop and to expose you to uses of instruments. Conduct the job with
interest and an attitude of learning.

You need to come well prepared for the job.

Work quietly and carefully (the whole purpose of experimentation is to make reliable
measurements!) and equally share the work with your partners.

All presentations of job and diagram should be neatly and carefully done.

Diagrams should be neatly drawn with pencil. Always display units.

Come equipped with scales, pencils etc.

Do not fiddle idly with apparatus. Handle instruments with care. Report any breakage to the
Instructor. Return all the equipment you have signed out for the purpose of your experiment.
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Syllabus
B. V. RAJU INSTITUTE OF TECHNOLOGY (AUTONOMOUS), NARSAPUR, MEDAK (DIST)
I Year B. Tech
L T/P/D C
- - /3 / - 2
ENGINEERING WORKSHOP
(Common to all branches)
Objective:
To familiarise with the basic manufacturing processes and to study the various tools and equipment used,
hands-on training is given in different sections. Essentially student should know the labour involved,
machinery or equipment necessary, time required to fabricate and also should be able to estimate the cost
of the product or job work.
TRADES FOR EXERCISES:
At least two exercises from each trade:
a. Carpentry: Middle lap T joint, cross lap joint, mortise and tenon T joint, Bridle T joint
b. Fitting: Square joint, V joint, half round joint, dovetail joint
c. Tin-Smithy: Tray, cylinder, hopper, funnel
d. Black Smithy: Simple exercises based on black smithy operations such as upsetting, drawing down,
punching, bending, swaging and fullering
e. House-wiring: wiring for ceiling rose and two lamps (bulbs) with independent switch controls with or
without looping, wiring for stair case lamp, wiring for a water pump with single phase starter.
f. Foundry: single pattern, double pattern
TRADES FOR DEMONSTRATION:
a. Plumbing
b. Machine Shop
c. Welding
d. Power tools in construction, wood working, electrical engineering and mechanical Engineering.
Outcomes
Basic practice sessions must be conducted in the trades mentioned and then two products of Industrial
application (with combination of different trades) may be produced with the available resources.
REFERENCE BOOKS:
1. Engineering Work shop practice for JNTU, V. Ramesh Babu, VRB Publishers Pvt. Ltd.
2. Work shop Manual / P.Kannaiah/ K.L.Narayana/ SciTech Publishers.
3. Engineering Practices Lab Manual, Jeyapoovan, SaravanaPandian, Vikas publishers
4. Dictionary of Mechanical Engineering, GHF Nayler, Jaico Publishing House.
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BLACKSMITHY
Blacksmithy or Forging is an oldest shaping process used
for the producing small articles for which accuracy in size is
not so important. The parts are shaped by heating them in an
open fire or hearth by the blacksmith and shaping them
through applying compressive forces using hammer.
Thus forging is defined as the plastic deformation of
metals
at
elevated temperatures into a predetermined size or shape using compressive forces exerted through some
means of hand hammers, small power hammers, die, press or upsetting machine. It consists essentially of
changing or altering the shape and section of metal by hammering at a temperature of about 980°C, at
which the metal is entirely plastic and can be easily deformed or shaped under pressure. The shop in
which the various forging operations are carried out is known as the smithy or smith’s shop.
Hand forging process is also known as black-smithy work which is commonly employed for
production of small articles using hammers on heated jobs. It is a manual controlled process even though
some machinery such as power hammers can also be sometimes used. Black-smithy is, therefore, a
process by which metal may be heated and shaped to its requirements by the use of blacksmith tools either
by hand or power hammer.
Forging by machine involves the use of forging dies and is generally employed for massproduction of accurate articles. In drop forging, closed impression dies are used and there is drastic flow
of metal in the dies due to repeated blow or impact which compels the plastic metal to conform to the
shape of the dies.
Applications of forging
Almost all metals and alloys can be forged. The low and medium carbon steels are readily hot forged
without difficulty, but the high-carbon and alloy steels are more difficult to forge and require greater care.
Forging is generally carried out on carbon alloy steels, wrought iron, copper-base alloys, aluminum alloys,
and magnesium alloys. Stainless steels, nickel-based super alloys, and titanium are forged especially for
aerospace uses.
FORGEABILITY
The ease with which forging is done is called forgeability. The forgeability of a material can also be
defined as the capacity of a material to undergo deformation under compression without rupture.
Forgeability increases with temperature up to a point at which a second phase, e.g., from ferrite to
austenite in steel, appears or if grain growth becomes excessive.
COMMON HAND FORGING TOOLS
For carrying out forging operations manually, certain
common hand forging tools are employed. These are
also called blacksmith’s tools, for a blacksmith is one
who works on the forging of metals in their hot state.
The main hand forging tools are as under.
Tongs
The tongs are generally used for holding work while
doing a forging operation. Various kinds of tongs are
shown in Figure.
a)
b)
c)
d)
Straight-lip fluted tongs are commonly used for holding square, circular and hexagonal bar stock.
Rivet or ring tongs are widely used for holding bolts, rivets and other work of circular section.
Flat tongs are used for mainly for holding work of rectangular section.
Gad tongs are used for holding general pick-up work, either straight or tapered.
Flatter
Flatter is shown in Fig. 14.7. It is commonly used in forging shop to give smoothness and accuracy to
articles which have already been shaped by fullers and swages.
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Swage
Swage is used for forging work which has to be reduced or finished to round, square or hexagonal form. It
is made with half grooves of dimensions to suit the work being reduced. It consists of two parts, the top
part having a handle and the bottom part having a square shank which fits in the hardie hole on the anvil
face.
Fuller
Fuller is used in forging shop for necking down a forgeable job. It is made in top and
bottom tools as in the case of swages. Fuller is made in various shapes and sizes
according to needs, the size denoting the width of the fuller edge
Punch
Punch is used in forging shop for making holes in metal part when it is at forging heat.
Rivet header
Rivet header (Fig. 14.7) is used in forging shop for producing rivets heads on parts.
Chisels
Chisels are used for cutting metals and for nicking prior to breaking. They may be hot or cold depending
on whether the metal to be cut is hot or cold. A hot chisel generally used in
forging shop is shown in Fig. 14.7. The main difference between the two is in
the edge. The edge of a cold chisel is hardened and tempered with an angle of
about 60°, whilst the edge of a hot chisel is 30° and the hardening is not
necessary. The edge is made slightly rounded for better cutting action.
Hand hammers
There are two major kinds of hammers are used in hand forging:
a. The hand hammer used by the smith himself and
b. The sledge hammer used by the striker.
Hand hammers may further be classified as (a) ball peen hammer, (b)
straight peen hammer, and (c) cross peen hammer.
Sledge hammers may further be classified as (a) Double face
hammer, (b) straight peen hammer, and (c) cross peen hammer.
Hammer heads are made of cast steel and, their ends are hardened and tempered. The striking face is made
slightly convex. The weight of a hand hammer varies from about 0.5 to 2 kg whereas the weight of a
sledge hammer varies from 4 to 10 kg
Set hammer
A set hammer generally used in forging shop is shown in Fig. 14.9. It is used for finishing corners in
shouldered work where the flatter would be inconvenient. It is also used for drawing out the gorging job.
Anvil
An anvil is a most
commonly tool used in
forging shop which is
shown in. It acts as a
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support for blacksmith’s work during hammering. The body of the anvil is made of mild steel with a tool
steel face welded on the body, but the beak or horn used for bending curves is not steel faced. The round
hole in the anvil called pritchel hole is generally used for bending rods of small diameter, and as a die for
hot punching operations. The square or hardie hole is used for holding square shanks of various fittings.
Anvils in forging shop may vary up to about 100 to 150 kg and they should always stand with the top face
about 0.75 mt. from the floor. This height may be attained by resting the anvil on a wooden or cast iron
base in the forging shop.
Swage block
Swage block generally used in forging shop is shown in figure. It is mainly used for heading, bending,
squaring, sizing, and forming operations on forging jobs. It is 0.25 mt. or even more wide. It may be used
either flat or edgewise in its stand.
FORGING OPERATIONS:
The following are the basic operations that may be performed by hand forging:
1. Drawing-down:
Drawing is the process of stretching the stock while reducing its cross-section locally. Forging the
tapered end of a cold is an example of drawing operation.
2. Upsetting:
It is a process of increasing the area of cross-section of a metal piece locally, with a corresponding
reduction in length. In this, only the portion to be upset is heated to forging temperature and the work is
then struck at the end with a hammer. Hammering is done by the smith (student) himself, if the job is
small, or by his helper, in case of big jobs, when heavy blows are required with a sledge hammer.
3. Fullering:
Fullers are used for necking down a piece of work, the reduction often serving as the starting
point for drawing. Fullers are made of high carbon steel in two parts, called the top and bottom fullers.
The bottom tool fits in the hardie hole of the anvil. Fuller size denotes the width of the fuller edge.
4. Flattering:
Flatters are the tools that are made with a perfectly flat face of about 7.5 cm square. These are
used for finishing flat surfaces. A flatter of small size is known as set-hammer and is used for finishing
near corners and in confined spaces.
5. Swaging:
Swages like fullers are also made of high carbon steel and are made in two parts called the top and
swages. These are used to reduce and finish to round, square or hexagonal forms. For this, the swages are
made with half grooves of dimensions to suit the work.
6. Bending:
Bending of bars, flats, etc., is done to produce different types of bent shapes such as angles, ovals,
circles etc. Sharp bends as well as round bends may be made on the anvil, by choosing the appropriate
place on it for the purpose.
7. Twisting:
It is also one form of bending. Sometimes, it is done to increase the rigidity of the work piece.
Small piece may be twisted by heating and clamping a pair of tongs on each end of the section to be
twisted and applying a turning moment.
Larger pieces may be clamped in a leg vice and twisted with a pair of tongs or a monkey wrench.
However, for uniform twist, it must be noted that the complete twisting operation must be performed in
one heating.
8. Cutting (Hot and Cold Chisels):
Chisels are used to cut metals, either in hot or cold state. The cold chisel is similar to fitter’s
chisel, except that it is longer and has a handle. A hot chisel is used for cutting hot metal and its cutting
edge is long and slender when compared to cold chisel. These chisels are made of tool steel, hardened and
tempered.
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9. Iron-Carbon Alloy:
If the carbon is less than 2% in the iron-carbon alloy, it is known as steel. Again, based on the
carbon content, it is called mild steel, medium carbon steel and high carbon steel. The heat treatment to be
given to these steels and their applications are shown in table below.
Carbon
Hardening
Tempering
Applications.
%
temp. 0C
temp. 0C
Mild Steel
Medium
Carbon steel
High Carbon
0.1
800-840
250-300
Chains, rivets, soft wire, sheet
0.25
800-840
250-300
Tube, rod, strip
0.5
800-840
250-300
Girders
0.6
800-840
250-300
Saws, hammers, smith’s and general
purpose tools
0.75
760-800
250-300
0.9
760-800
250-300
1.0
760-800
250-300
1.2
720-760
250-300
1.35
720-760
250-300
1.5
720-760
250-300
Cold chisels, smith’s tools shear blades,
table cutlery
Taps, dies, punches, hot shearing blades
Drills, reamers, cutters, blanking and
slotting tools, large turning tool
Small cutters, lathe and engraving tools,
files drills
Extra hard, planning, turning and slotting
tools, dies and mandrels
Razor blades
NOTE: The forging produced either by hand forging or machine forging should be heat treated.
The following are the purposes of heat treatment:
i.
To remove internal stresses set-up during forging and cooling.
ii.
To normalize the internal structure of the metal.
iii.
To improve machinability.
iv.
To improve mechanical properties, strength and hardness.
SAFE PRACTICES:
1. Hold the hot work downwards close to the ground, while transferring from the hearth to anvil, to
minimize danger of burns; resulting from accidental collisions with others.
2. Use correct size and type of tongs to fit the work. These should hold the work securely to prevent
its bouncing out of control from repeated hammer blows.
3. Care should be exercised in the use of the hammer. The minimum force only should be used and
the flat face should strike squarely on the work; as the edge of the hammer will produce heavy
bruising on hot metal.
4. Water face shield when hammering hot metal.
5. Wear gloves when handling hot metal.
6. Wear steel-toed shoes.
7. Ensure that hammers are fitted with tight and wedged handles.
Page 9
Page 10
EXP: 1
S-Hook
Date
Aim: To make an S-hook from a given round rod, by following hand forging operation.
Tools required:
Smith’s forge, Anvil, 500gm and I kg ball-peen hammers, Flatters, Swage block, Half round tongs, Pickup tongs, Cold chisel.
Sequence of operations:
1. One end of the bar is heated to red hot condition in the smith’s
forge for the required length.
2. Using the pick-up tongs; the rod is taken from the forge, and
holding it with the half round tongs, the heated end is forged into
a tapered pointed end.
3. The length of the rod requires for S-hook is estimated and the
excess portion is cut-off, using a cold chisel.
4. One half of the rod towards the pointed end is heated in the forge
to red hot condition and then bent into circular shape as shown.
5. The other end of the rod is then heated and forged into a tapered
pointed end.
6. The straight portion of the rod is finally heated and bent into
S- HOOK
circular shape as required.
7. Using the flatter, the S-hook made as above, is kept on the anvil
and flattened so that, the shape of the hook is proper.
NOTE: In-between the above stage, the bar is heated in the smith’s forge, to facilitate forging
operations.
Result:
The S-hook is thus made from the given round rod; by following the stages mentioned above.
Precautions:
1. Hold the job carefully while heating and hammering
2. Job must be held parallel to the face of the anvil.
3. Wear steel-toed shoes.
4. Wear face shield when hammering the hot metal
5. Use correct size and type of tongs to fit the work.
Page 11
EXP: 2
Square Rod
Date
Aim: To make a Square rod from a given round rod, by following hand forging operation.
Tools required:
Smith’s forge, Anvil, 500gm and I kg ball-peen hammers, Flatters, Swage block, Half round tongs, Pickup tongs, Cold chisel.
1. Take the raw material from stock i.e.,
mild steel 10 mm round shaped, cut the
length of 50 mm.
2. Handle specimen with round tong and
heat in blacksmith’s forge upto the part
appears as red cherry color code.
3. The required piece heated upto it gets the
recrystalization temperature.
4. The part is taken out from the forge and
blow with sledge hammer for obtaining
the square shape on all edges.
5. The hammering is done on the anvil.
6. The above mentioned all steps are done,
after the specimen bent in required shape.
7. Check the dimensions after cooling the job by quenching process.
NOTE: In-between the above stage, the bar is heated in the smith’s forge, to facilitate forging
operations.
Result:
The square rod is thus made from the given round rod.
Precautions:
1.
2.
3.
4.
5.
Hold the job carefully while heating and hammering
Job must be held parallel to the face of the anvil.
Wear steel-toed shoes.
Wear face shield when hammering the hot metal
Use correct size and type of tongs to fit the work.
Page 12
CARPENTRY
Carpentry is the process of shaping Timber, using hand tools. The products produced are used in
building construction, such as doors and windows, furniture manufacturing, patterns for moulding in
foundries, etc. Carpentry work mainly involves the joining together of wooden pieces and finishing the
surfaces after shaping them. Hence, the term joining is also used commonly for carpentry. A student
studying the fundamentals of wood working has to know about timber and other carpentry materials,
wood working tools, carpentry operations and the method of making common types of joints.
Materials Used in Carpentry:
Basic materials used in carpentry shop are timber and plywood. Auxiliary materials used are nails, screws,
adhesives, paints, varnishes, etc.
Timber:
Timber is the name given to wood obtained from exogenous (outward growing) trees. In these trees, the
growth is outward from the centre, by adding almost concentric layers of fresh wood every year known as
annual rings. After the full growth, these trees are cut and sawed to convert into rectangular sections of
various sizes for engineering purposes.
Timber is available in market in various shapes and size. The common shapes and sizes an: given below:
1. Log: This is the trunk of die tree which is tree from branches.
2. Balk: This is the log after sawing roughly to square cross section.
3. Deal: This is the log after sawing into rectangular cross section of width about 225 mm and
thickness up to 100 mm.
4. Plank: This is the timber piece having width more than 275 mm and thickness 50 lo 150 mm.
5. Board: This is the timber piece below 50 mm in thickness and above 125 mm in width,
6. Batten: This is the timber piece below 175 mm in width and thickness between 30 mm to 50 mm
in thickness.
7. Scantlings: These are timber pieces of various assorted and nonstandard sizesother than the types
given above.
Classification of Wood
The timber used for commercial purposes can he divided into two classes as soft wood and hard wood
Soft wood
A soft wood is light in weight and light colored. They may
have distinct annual rings but the medullar rays (radial lines)
are not visible and the color of the sap wood (outer layers) is
not distinctive from the heart wood (inner layers). These
woods cannot resist stresses developed across their fibers;
hence, not suitable for wood working.
Hard wood
In this type of wood the annual rings are compact and thin and
the medullar rays (radial lines} are Visible in most cases Figure6.1. Hard woods are nearly equally strong
both along and across the fibers. Hand wood is the material used for wood working
Classification of timber
According to the manner of growth of trees, timber can be classified as
i) Exogenous or out ward growing
ii) Endogenous or in ward growing
i) Exogenous or out ward growing
In exogenous trees the growth take place from the centre by the addition of concentric layers
of fresh wood every year, known as annual rings. These varieties of trees are suitable for building and
other engineering uses the exogenous trees are again classified as
a) Conifers or ever green trees
b) Deciduous or broad leaf trees
Page 13
The conifer give soft woods and the deciduous gives hard wood common example of hard wood are
Sal, teak, rose wood, sandal, shisham, oak beach, ash ebony, mango, neem, babool, etc., soft wood
include kail pine, deodar chair, walnut seemal etc.
ii) Endogenous or in ward growing timber
These trees grow in wards i.e. .every fresh layer of sap wood is added inside instead of outside cane,
bamboo, coconut
Seasoning
Seasoning of wood carried out for removing the sap and reducing the moisture content the presence of
sap and moisture will render the wood unsuitable for engineering works due to uneven shrinkage,
crack, wrapping and decay.
Different methods of seasoning
1. Air seasoning or Natural seasoning
2. Water seasoning
3. Electrical seasoning
4. Kiln seasoning
Ply wood
Thick sheet formed by pasting veneers of wood is called ply. Three or more plys joined by glues is
called plywood. The grains of adjacent layers are kept at right angle to each other in order to get better
strengthening both directions the outer layer are called facing plys and good hard wood veneers are used
for this inner ones are called core plys and low quality wood is used for this the ply wood is made by
either cold pressing or hot pressing.
Tools for wood working
The principle hand tools used in a carpentry workshop can be classified into
i) Marking and measuring tool
ii) Cutting tool
iii) Planning tool
iv) Boring tool
v) Striking tool
vi) Holding tool
Marking and measuring tool
a) Rules
Rules are used for measuring dimensions. For measuring and setting out
dimensions various types of rules are used in carpentry shop. Steel RuleStainless Steel Rule of length 30cm and 60cm. Flexible Measuring Rulefor measuring large dimensions as well as curved or angular surface
dimensions.
b) Straight Edge and Squares
This is a machined flat piece wood or metal having perfectly straight and parallel edges.
c) Steel Tape: It is used for large dimensions, such as marking on boards and checking the overall
dimensions of the work.
e) Gauges
Gauges are used to mark lines parallel to the edges of a wooden piece. It mainly consists of a wooden
stem sliding inside a wooden stock. The stem carries a steel point for marking lines. The stock
position on the stem can be varied and fixed rigidly by tightening the thumb screw.
Fig. Marking Gauge
Page 14
To mark a line parallel to an edge the gauge stock is held freely against the edge and pushed along it,
pressing the steel points to the surface
Fig. Mortise Gauge
c) Try square
Try square consists of rectangular steel blade fixed rigidly to cast iron stock. The length of blade
varies from 150mm to 300mm.
Marking Knife or Scriber
Marking Knives are used to convert the pencil lines drawn on the wooden surface into deep scratch
lines on the surface. They are made of steel with a sharp point at one end and flat blade at the other end.
Fig. Marking Knife
Fig. Try Square
Bevel Square: it is also called sliding level. It is an adjustable try-square used
for measuring/marking angles between 00 and 1800.
VI Holding tools
a) Work Bench
This is a table of having size and raised construction made of hard wood.
The size ranges from 50- 80 cm in length and about 90cm in width. Two
Fig. Bevel Square
or four carpenters can work at a time on the work
bench.
Carpenters Bench Vice
It consists of jaw fixed on the table side and movable jaw
kept in position by means of screw and handle. The
body of vice is made of cast iron or steel. The jaws are
lined with hard wood which can be removed when it is
damaged.
Fig. Work Bench with Bench Hook
The screw moves inside the fixed half nut which can be
engaged or disengaged by operating the lever. This is made up of a bar of steel. The work is clamped
between jaws by rotating the screw using the handle. It is used for clamping glued pieces or holding the
work piece of larger size together for various operations.
a) Sash-cramp
Page 15
b) C Clamp: The clamp of the shape of letter C or G is used to clamp short pieces together as the
bar clamp. These clamps are available is sizes varying from 70 mm to 800 mm. it is used for
holding the planks after gluing
Fig. Carpenters Bench Vice
Fig. C- Clamp
Fig. Bar or T-Cramp
Bar or T-cramp: it consists of a steel bar fitted with a threaded spindle and an adjustable shoe. It is used
for holding the glued pieces tightly or holding firmly two or more unglued pieces for fitting dowels or
doing other operations on them in assembled position.
II
Cutting tools
a) Saws
Saw is a cutting tool which has teeth on one edge and cutting is affected by reciprocating motion
of the edge relative to the work piece. Cutting occurs during the forward motion; such a saw is called
push type saw, the cutting occurs during the backward motion.
i.
Hand Saw- This saw is used for short straight cuts. It has a blade of 25-40cm length 610cm width. The number of teeth per cm length ranges from 3-5.
ii.
Tenon Saw (Back Saw)- It has a parallel blade of 25-40cm length and 6-10cm width. The
number of teeth per cm length ranges from 5-8.
b) Chisels
The common type of chisels used is briefly explained below.
i.
Firmer Chisels- they are most common and general purpose chisel used by a carpenter. They have
flat blade of 15-50mm width and 125mm length.
ii.
Dove Tail Chisel (beveled edge firmer chisel) - These chisels are used for fine and delicate works
as well as for cutting corners.
iii.
Mortise chisel – These chisels are used for heavy and deep cut to remove large quantity of
wood. These chisels have width of about 15mm but the blade thickness may range from 615mm.
Page 16
Fig. Saws
Fig. Parts of a Chisel
Fig. Cross-cut Saw
Fig. Rip Saw
Fig. Parts of Saw
Fig. Types of Chisels
III Planing Tools
Page 17
Planing tool is used to smoothen the wooden surfaces.
a) Wooden jack plane
This is the most commonly used plane in carpentry shop. The main part of a wooden jack plane is a
wooden block called sole, in which steel blade having knife edge is fixed at an angle with the help of
wooden edge. The angle of the blade is kept about 45 ° to bottom surface of the blade.
b)
Metal Jack Plane
It serves the same purpose as the wooden jack plane but
facilitates a smoother operations and better finish. The
body of a metal jack plane is made from a grey iron
casting with the side and sole machined and ground to
better finish.
DRILLING AND BORING TOOLS:
a) Bradawl: It is a hand operated tool, used to bore
small holes for starting a screw or large nail.
Fig. Gimlet Drill
Fig. Plane
b) Carpenters brace: it is used for rotating auger bits,
twist drills, etc., to produce holes in wood. In some designs, braces are made with ratchet device.
c) Auger bit: it is the most common tool used for making holes in wood. During
drilling, the lead screw of the bit guides into the wood, necessitating only moderate
pressure on the brace. The helical flutes on the surface carry the chips to the outer
surface.
d) Hand drill: carpenter’s brace is used to make relatively large size holes; whereas
hand drill is used for drilling small holes. A straight shank drill is used with this tool. It
is small, light in weight and may be conveniently used than the brace. The drill bit is
clamped in the chuck at its end and is rotated by a handle attached to gear and pinion
arrangement.
e) Gimlet: it has cutting edges like a twist drill. It is used for drilling large diameter
holes with the hand pressure.
Striking Tools
a)
Mallet
This is wooden headed hammer of round or rectangular
section. The striking face is made flat. Mallet is used for
the cutting tools and has wooden handle.
cross
striking
b) Claw Hammer
Mallet
This is a hammer having steel head and wooden handle. The flat face of the head is used toFig.
drive
nails
and claw portion for extracting nails out of the wood.
Page 18
Fig. Pincer
Fig. Claw Hammer
c) Pincer: it is made of two forged steel arms with a hinged joint and is used for pulling-out small nails
from wood. The inner faces of the pincer jaws are bevelled and the outer faces are plain. The end of one
arm has a ball and the other has a claw. The bevelled jaws and the claw are used for pulling out small
nails, pins and screws from the wood.
d) Screw Driver: it is used for driving wood screws into wood or unscrewing them. The length of a screw
driver is determined by the length of the blade. As the length of the blade increases, the width and
thickness of the tip also increase.
Fig. Screw Driver
Wood rasp files: it is a finishing tool used to make the wood surface smooth, remove sharp edges, and
finish fillets and other interior surfaces. Sharp cutting teeth are provided on its surface for the purpose.
This file is exclusively used in wood work.
Fig. Wood Rasp files
Page 19
EXPT.NO:1
DOVETAIL LAP JOINT
DATE:
AIM:to make a dovetail lap joint.
MATERIALS REQUIRED: Teak wood (30mm*150mm*50mm)
TOOLS AND EQUIPMENT
USED:
1. Steel rule
2. Try square
3. Marking guage
4. Rip saw
5. Tenon saw
6. Mortise chisel
7. Mallet
8. Jack plane
9. Wood rasp file
OPERATIONS TO BE CARRIED
OUT:
1. Planning
2. Marking
3. Sawing
4. Chiseling
5. Finishing
PROCEDURE:
1. The wooden pieces are made into two halves and are checked for dimensions.
2. One side of pieces is planned with jack plane and for strraightness.
3. An adajacent side is planned and checked for squareness with a try square.
4. Marking guage is set and lines are marked at 40-50 mm to make the thickness and width
according to given figure.
5. The excess material is planned to correct size.
6. Using tenon saw, the portions to be removed are cut in both the pieces
7. The excess material in X is chiseled with mortise chisel.
8. The excess material in Y in chiseled to suit X
9. The end of both the pieces is chiseled to exact lengths.
PRECAUTIONS:
1. Wood should be free from moisture
2. Marking is done with out parallax error
3. Care shoukd be taken while chiseling
4. Matching of X and Y pieces should be tight.
RESULT:
The dovetail lap joint is made success fully.
EXPT.NO:2
CROSS HALF LAP JOINT
DATE:
AIM:to make a cross half lap joint.
MATERIALS REQUIRED: Teak wood (30mm*150mm*50mm)
TOOLS AND EQUIPMENT USED:
Page 20
1.
2.
3.
4.
5.
6.
7.
8.
9.
Steel rule
Try square
Marking guage
Rip saw
Tenon saw
Mortise chisel
Mallet
Jack plane
Wood rasp file
OPERATIONS TO BE
1.
2.
3.
4.
5.
CARRIED OUT:
Planning
Marking
Sawing
Chiseling
Finishing
PROCEDURE:
1.
2.
3.
4.
5.
6.
7.
8.
9.
The wooden pieces are made into two halves and are checked for dimensions.
One side of pieces is planned with jack planeand for strraightness.
An adajacent side is planned and checked for squareness with a try square.
Marking guage is set and lines are marked at 40-50 mm to make the thickness and width
according to given figure
The excess material is planned to correct size.
Using tenon saw, the portions to be removed are cut in both the pieces
The excess material in X is chiseled with mortise chisel.
The excess material in Y in chiseled to suit X
The end of both the pieces is chiseled to exact lengths.
PRECAUTIONS:
1.
2.
3.
4.
Reaper should be free from moisture
Marking is done with out parallax error
Care shoukd be taken while chiseling
Matching of x and y pieces should be tight.
RESULT: The cross half lap joint is made success fully.
Page 21
FITTING
The term fitting, is related to assembly of parts, after bringing the dimension or shape to the required size
or form, in order to secure the necessary fit. The operations required for the same are usually carried out
on a work bench, hence the term bench work is also added with the name fitting.
The bench work and fitting plays an important role in engineering. Although in today's industries
most of the work is done by automatic machines which produces the jobs with good accuracy but still it
(job) requires some hand operations called fitting operations. The person working in the fitting shop is
called fitter
FITTING TOOLS:
Fitting shop tools are classified as below:
 Work Holding Devices/ Clamping Tools.
 Measuring and Marking Tools.
 Cutting Tools.
 Striking Tools.
 Drilling Tools.
 Threading Tools.
I. WORK HOLDING DEVICES /CLAMPING TOOLS:
1. Work Bench
A fitting process can be done at various places, but
most of the important operations of fitting are generally
carried out on a table called work bench.
The work bench is a strong, heavy and rigid table made
up of hard wood.
The size of the work bench required is about 150 to 180
cm length, nearly 90 cm width and approximately 76 to
84 cm height.
2. BENCH VICE:
It is firmly fixed to the bench with the help of nuts and bolts. It consists of a cast Iron body and cast
iron jaws. Two jaw plates are fitted on both the jaws. The holding surface of the jaw plates is knurled in
order to increase the gipping. Jaw plates are made up of carbon steel and are wear resistant. One jaw is
fixed to the body and the second slides on a square threaded screw with the help of a handle.
The jaws are opened upto required length; job is placed in the two jaws and is fully tightened with the
help of handle. Handle is used to move the movable jaw
Page 22
3. V Block
In V Block, V grooves are provided to hold the round objects longitudinally. The screw of the
clamp applies the holding pressure. When the handle is rotated there is movement in the screw.
II. MEASURING TOOLS
1. Steel Rule
These are made up of stainless steel and are available in many sizes ranging from 1/2 ft. to 2 ft. These
are marked in inches or millimetres. All the faces are machined true. The edges of steel rule should be
protected from rough handling.
2. Calipers
These are generally used to measure the inside or outside diameters. Different types are:
i. Outside Caliper: It is used to measure the outside dimensions.
ii. Inside Caliper: It is used to measure the inside dimensions.
iii. Spring Caliper: Spring is provided to apply the pressure and lock nut is provided to lock any
desired position.
iv. Hermaphrodite, Jenny or Oddleg Caliper: One leg is bent at the tip inwardly and the other has a
straight pointed end. It is used to scribe lines parallel to the straight edges.
Fig. Calipers
3. Vernier Caliper: It is used for measuring the outer dimensions of round, flat, square components and
also the inner size of the holes and bore. A narrow blade is used to measure the depth of bar slots etc. The
reading accuracy in metric system is 0.02 mm and British system it is 0.001”. It is made of stainless steel.
Page 23
III. MARKING TOOLS:
1. Surface Plate
It is used for testing the flatness, trueness of the
surfaces. It is made up of cast iron or graphite. Its upper
face is planed to form a very smooth surface. It is also
used in scribing work.
While not in use, it should be covered with a wooden
cover.
2. Angle Plate
It is made up of cast iron in different sizes; it has two planed surfaces
at right angles to each other and has various slots in each surface to
hold the work by means of bolts and clamps.
Never do hammering on the angle plate to fasten (lighten) the nuts
and bolts.
3. Scriber and Surface Gauge
It consists of a cast iron bass on the center of which a steel rod is fixed vertically. Scriber is made
up of high carbon steel and is hardened from the front edge. It is used for locating the centres of
round bars or for marking of the lines.
Fig. Scriber and Surface Gauge
4. Punches
Punches are used for marking purposes. Dot punches are used for marking dotted line and centre
punch is used to mark the centre of hole before drilling. Punches are made up of high carbon steel
or high speed steels. One end is sharpened. Hammering is done on the second end while working.
For dot punch, angle of the punching end is 60 degree while in centre punch; angle of punching
end is 90 degree.
Page 24
5. Try Square
It is used for checking squareness of two surfaces. It consists of a blade
made up of steel, which is attached to a base at 90 degree. The base is
made up of cast iron or steel. It is also used to mark the right angles and
measuring straightness of surfaces. Never use try square as a hammer.
6. Vernier Height gauge:
A Vernier height gauge consists of a heavy base, a graduated beam, a
sliding head with Vernier sliding jaws holding the scriber and a fine
adjustment clamp. It is similar to large Vernier calipers in construction,
except that it consists of a heavy base which allows the gauge to stand
upright instead of a fixed jaw in a Vernier. The movable jaw of Vernier
height gauge consists of a projection or extension which is levelled to
sharp edge for scribing lines at any required height.
METHOD OF MARKING
Marking means setting out dimensions with the help of a working
drawing or directly transferring them from a similar part. The procedure
Fig. Vernier height gauge
of marking is as follows:
A-Fine Adjustment of nut B-Vernier
1. The surface to be marked is coated with the paste of chalk or red
slide C-Scriber clamp screw D – Scriber E
– Vernier Scale F – Main Scale G – Base
lead and allowed to dry.
X,Y – Lock Screws
2. Then the work is held In a holding device depending upon shape
and size. If it is flat, use surface plate, if it is round use V block and clamp, else use angle plate
etc.
3. Lines in horizontal direction are scribed by means of a surface gauge. Lines at right angles can be
drawn by turning the work through 90 degree and then using the scriber. If true surface is
available, try square can also be used.
4. The centre on the end of a round bar can be located by using an odd leg caliper, surface gauge etc.
5. The circles and arcs on a flat surface are marked by means of a divider.
6. After the scribing work is over, indentations on the surface are made using dot punch and
hammer.
IV. CUTTING TOOLS
1. Hacksaw
Hacksaw is used for cutting of
rods, bars, pipes, flats etc. It
consists of a frame, which is
made from mild steel. The
blade is placed inside the
frame and is tightened with
the help of a flange nut. The
blade is made up of high
carbon steel or high speed
steel.
Fig. Hand Hacksaws
The points of the teeth are bent in a zig-zag
fashion, to cut a wide groove and prevent the body
Page 25
of the blade from rubbing or jamming in the saw cut. The teeth of the blades are generally forward cut so
in the case, pressure is applied in the forward direction only.
Depending upon the direction of cut, blades are classified as:
o Forward cut
o Backward cut.
Depending upon the pitch of the teeth (Distance between the two consecutive teeth) blades is classified as:
 Coarse (8-14 teeth per Inch)
 Medium (16-20 teeth per inch)
 Fine (24-32 teeth per inch)
2. Files
Files are multi points cutting tools. It is used to remove the material
by rubbing it on the metals. Files are available in a number of sizes,
shapes and degree of coarseness.
Classification of files
i. On the basis of length
4”,6”,8”,12”
ii. On the basis of grade:
 Rough (R)(20 teeth per inch)
 Bastard (B)(30 teeth per inch)
 Second cut (Sc) (40 teeth per inch)
 Smooth file (S)(50 teeth per inch)
 Dead smooth (DS)(100 teeth per inch)
Rough and bastard files are the big cut files. When the material removal is more, these files are used.
These files have bigger cut but the surface produced Is rough.
Dead smooth and smooth files have smaller teeth and used for finishing work. Second cut file has
degree of finish in between bastard and smooth file.
iv. On the basis of number of cuts:
 Single cut files.
 Double cut files.
 Rasp files.
In single cut files the teeth are cut in parallel rows at an angle of 60 degree to the face. Another row of
teeth is added in opposite direction in case of double cut files. Material removal is more in case of
double cut files.
iii. On the basis of shape and size:
The length of the files varies from 4' to 14*. The various shapes of cross-section available are hand
file, flat file, triangular, round; square, half round, knife-edge, pillar, needle and mill file.
Page 26
a. Flat file: This file has parallel edges for about two-thirds of the length and then it tapers in width
and thickness. The faces are double cut while the edges are single cut.
b. Hand file: for a hand file the width is constant throughout, but the thickness tapers as given in flat
file. Both faces are double cut and one edge is single cut. The remaining edge is kept uncut in
order to use for filing a right-angled corner on one side only.
c. Square file: It has a square cross-section. It is parallel for two-thirds of its length and then tapers
towards the tip. It is double cut on all sides. It is used for filing square corners and slots.
d. Triangular file: It has width either parallel throughout or upto middle and then tapered towards
the tip. Its section is triangular (equilateral) and the three faces are double cut and the edges single
cut. It is used for filing square shoulders or comers and for sharpening wood working saws.
e. Round file: It has round cross-section. It carries single cut teeth all round its surface. It is
normally made tapered towards the tip and is frequently known as rat-tail file. Parallel round files
having same diameter throughout the length are also available. The round files are used for
opening out holes, producing round comers, round-ended slots etc.
f. Half-round file: Its cross-section is not a true half circle but is only about one-third of a circle.
The width of the file is either parallel throughout or upto middle and then tapered towards the tip.
The flat side of this file is always a double cut and curved side has single cut. It is used for filing
curved surfaces.
g. Knife edge file: It has a width tapered like a knife blade and it is also tapered towards the tip and
thickness. It carries double cut teeth on the two broad faces and single cut teeth on the edge. It is
used for finishing sharp corners of grooves and slots
h. Diamond file: Its cross-section is like a diamond. It is used for special work.
i. Needle file: These are thin small files having a parallel tang and a thin, narrow and pointed blade
made in different shapes of its cross-section to suit the particular need of the work. These are
available in sizes from 100 mm to 200 mm of various shapes and cuts. These files are used for
filing very thin and delicate work.
Methods of filing
The following are the two commonly used methods of filing:
1. Cross-filing
2. Draw filing.
Cross - filing. Refer Fig. (a).
This method is used for efficient removal of maximum amount of
metal in the shortest possible time. It may be noted that the file must remain
horizontal throughout the stroke (long, slow and steady) with pressure only
applied on the forward motion.
Draw filing. Refer Fig. (b)
This method is used to remove file marks and for finishing operations. Here, the
file is gripped as close to the work as possible between two hands. In this filing
method, a fine cut file with a flat face should be used.
FILE CARD:
It is a device fashioned like a wire brush used to clean dirt and chips
from the teeth of a file. When particles of metal clog the teeth the file is
said to the pinned, a condition that causes scratching of the surface of
the work. Files, therefore, require cleaning by means of a file card or
by dislodging the material between the teeth by means of a piece of
soft iron, copper, brass, tin plate and so on, sharpened at the end.
Hardened steel should never be used
Fig. File Card
Page 27
Page 28
EXPT.NO: 01
SQUARE CUTTING
AIM: To make a Square fit from the given mid steel pieces.
MATERIALS REQUIRED: mild steel flat (40*40*3mm).
TOOLS AND EQUIPMENT REQUIRED:
1.6”try square
2. 6”sriber
3. Odd leg caliper
3.12”hack saw Frame
4 Blades (12 TPI)
5. 10”rough file
6. 10”smooth file
7. 10”Square file
8. Dot punch
9. Ball peen hammer (0.5 Ib).
10. Steel Rule
Sequence of OPERATIONS:
1. Filling
2. Marking
3. Punching
4. Sawing
5. Filling
6. Finishing
Date
PROCEDURE:
1. The given mild steel flat piece is checked for given dimensions.
2. One edge of given is filled to straightness with rough and smooth files and checked with try square.
3. An adjacent is also filled such that is square to first edge and checked with try square.
4. Wet chalk is applied on one side of the flat and dried for making.
5. Lines are marked according to given figure, using odd leg caliper and steel rule.
6. using the dot punch are made along the marked lines.
7. The excess materials removed from the remaining two edges with try square level up to half of the
marked dots.
8. Finally buts are removed by the filling on the surface of the fitted job.
PRECAUTIONS:
1. The perpendicularity of face ends edges is checked perfectly by using try square.
2. Finishing is given by using only with smooth files.
3. Marking is done without parallax error.
RESULT: The Square cutting is done successfully
Page 29
EXPT.NO: 02
V-FITTING
AIM: To make a V-Fit from the given mid steel pieces.
MATERIALS REQUIRED: Mild steel flat (40*40*3mm).
1.6”try square
2. 6”sriber
3. Odd leg caliper
3.12”hack saw Frame
4 Blades (12 TPI)
5.10”rough file
6.10”smooth file
7.10”triangle file
8. Knife Edge file
9. Dot punch
10. Ball peen hammer (0.5 Ib)
11. Steel Rule
Sequence of Operations:
1. Filling
2. Marking
3. Punching
4. Sawing
5. Filling
6. Finishing
PROCEDURE:
1. The given mild steel flat piece is checked for given dimensions.
2. One edge of given is filled with rough and smooth files and checked with try square for
straightness.
3. An adjacent edge is also filled such that it is square to first edge and checked with try square.
4. Wet chalk is applied on one side of the flat and dried for marking.
5. Lines are marked according to given figure, using odd leg caliper and steel rule.
6. Using the dot punch, punches are made along the marked lines.
7. The excess materials removed from the remaining two edges with try square level up to half of
the marked dots.
8. Finally buts are removed by the filling on the surface of the fitted job.
PRECAUTIONS:
1. The perpendicularity of face ends edges is checked perfectly by using try square.
2. Finishing is given by using only with smooth files.
3. Marking is done without parallax error.
RESULT:
The V-fit is done successfully.
Page 30
FOUNDRY
PATTERN
A pattern is a model or the replica of the object (to be casted). It is embedded in molding sand and suitable
ramming of molding sand around the pattern is made. The pattern is then withdrawn for generating cavity
(known as mold) in molding sand.
COMMON PATTERN MATERIALS
The common materials used for making patterns are wood, metal, plastic, plaster, wax or Mercury.
TYPES OF PATTERN
The types of the pattern and the description of each are given as under.
1. One piece or solid pattern 2. Two piece or split pattern 3. Cope and drag pattern 4. Three-piece or
multi- piece pattern 5. Loose piece pattern 6. Match plate pattern 7. Follow board pattern 8. Gated pattern
9. Sweep pattern 10. Skeleton pattern 11. Segmental or part pattern
1. Single-piece or solid pattern: Solid pattern is made of single piece without joints, partings lines or
loose pieces. It is the simplest form of the pattern. Typical single piece pattern is shown in Fig. 10.1.
2. Two-piece or split pattern: When solid pattern is difficult for withdrawal from the mold cavity, then
solid pattern is split in two parts. Split pattern is made in two pieces which are joined at the parting line by
means of dowel pins. The splitting at the parting line is done to facilitate the withdrawal of the pattern. A
typical example is shown in Fig. 10.2
Fig. Single Piece Pattern
Fig. Two Piece Pattern
MOLDING SAND
The general sources of receiving molding sands are the beds of sea, rivers, lakes, granular elements of
rocks, and deserts.
Molding sands may be of two types namely natural or synthetic. Natural molding sands contain sufficient
binder. Whereas synthetic molding sands are prepared artificially using basic sand molding constituents
(silica sand in 88-92%, binder 6-12%, water or moisture content 3-6%) and other additives in proper
proportion by weight with perfect mixing and mulling in suitable equipments.
Binder
In general, the binders can be either inorganic or organic substance. The inorganic group includes clay
sodium silicate and port land cement etc. In foundry shop, the clay acts as binder which may be Kaolonite,
Ball Clay, Fire Clay, Limonite, Fuller’s earth and Bentonite. Binders included in the organic group are
dextrin, molasses, cereal binders, linseed oil and resins like phenol formaldehyde, urea formaldehyde etc.
Organic binders are mostly used for core making.
Among all the above binders, the bentonite variety of clay is the most common. However, this clay alone
cannot develop bonds among sand grins without the presence of moisture in molding sand and core sand.
Additives
Page 31
Additives are the materials generally added to the molding and core sand mixture to develop some special
property in the sand. Some common used additives for enhancing the properties of molding and core
sands are discussed as under.
1. Coal dust: Coal dust is added mainly for producing a reducing atmosphere during casting.
2. Corn flour: It belongs to the starch family of carbohydrates and is used to increase the collapsibility
of the molding and core sand
3. Dextrin: Dextrin belongs to starch family of carbohydrates that behaves also in a manner similar to
that of the corn flour. It increases dry strength of the molds.
4. Sea coal: Sea coal is the fine powdered bituminous coal which positions its place among the pores of
the silica sand grains in molding sand and core sand
5. Wood flour: This is a fibrous material mixed with a granular material like sand; its relatively long
thin fibers prevent the sand grains from making contact with one another.
6. Silica flour: It is called as pulverized silica and it can be easily added up to 3% which increases the
hot strength and finish on the surfaces of the molds and cores
KINDS OF MOULDING SAND
Molding sands can also be classified according to their use into number of varieties which are described
below.
1. Green sand: Green sand is also known as tempered or natural sand which is a just prepared mixture
of silica sand with 18 to 30 percent clay, having moisture content from 6 to 8%. The clay and water
furnish the bond for green sand. It is fine, soft, light, and porous.
2. Dry sand: Green sand that has been dried or baked in suitable oven after the making mold and cores,
is called dry sand. It possesses more strength, rigidity and thermal stability.
3. Loam sand: Loam is mixture of sand and clay with water to a thin plastic paste. Loam sand possesses
high clay as much as 30-50% and 18% water.
4. Facing sand: Facing sand is just prepared and forms the face of the mould. It is directly next to the
surface of the pattern and it comes into contact molten metal when the mould is poured. Initial coating
around the pattern and hence for mold surface is given by this sand. This sand is subjected severest
conditions and must possess, therefore, high strength refractoriness.
5. Backing sand: Backing sand or floor sand is used to back up the facing sand and is used to fill the
whole volume of the molding flask.
6. Parting sand: Parting sand without binder and moisture is used to keep the green sand not to stick to
the pattern and also to allow the sand on the parting surface the cope and drag to separate without
clinging
7. Core sand: Core sand is used for making cores and it is sometimes also known as oil sand. This is
highly rich silica sand mixed with oil binders such as core oil which composed of linseed oil, resin,
light mineral oil and other bind materials.
PROPERTIES OF MOULDING SAND
The basic properties required in molding sand and core sand are described as under.
1. Refractoriness: Refractoriness is defined as the ability of molding sand to withstand high
temperatures without breaking down or fusing thus facilitating to get sound casting. It is a highly
important characteristic of molding sands. Refractoriness can only be increased to a limited extent
2. Permeability: It is also termed as porosity of the molding sand in order to allow the escape of any air,
gases or moisture present or generated in the mould when the molten metal is poured into it. All these
gaseous generated during pouring and solidification process must escape otherwise the casting
becomes defective
3. Cohesiveness: It is property of molding sand by virtue which the sand grain particles interact and
attract each other within the molding sand
Page 32
4. Green strength: The green sand after water has been mixed into it, must have sufficient strength and
toughness to permit the making and handling of the mould. For this, the sand grains must be adhesive,
i.e. thev must be capable of attaching themselves to another body
5. Dry strength: As soon as the molten metal is poured into the mould, the moisture in the sand layer
adjacent to the hot metal gets evaporated and this dry sand layer must have sufficient strength to its
shape in order to avoid erosion of mould wall during the flow of molten metal
6. Flowability or plasticity: It is the ability of the sand to get compacted and behave like a fluid. It will
flow uniformly to all portions of pattern when rammed and distribute the ramming pressure evenly all
around in all directions
7. Adhesiveness: It is property of molding sand to get stick or adhere with foreign material such sticking
of molding sand with inner wall of molding box
8. Collapsibility: After the molten metal in the mould gets solidified, the
sand mould must be collapsible so that free contraction of the metal
occurs and this would naturally avoid the tearing or cracking of the
contracting metal.
HAND TOOLS USED IN FOUNDRY SHOP
Hand riddle: It consists of a screen of standard circular wire mesh
equipped with circular wooden frame. It is generally used for
cleaning the sand for removing foreign material such as nails, shot
metal, splinters of wood etc. from it. Even power operated riddles are
available for riddling large volume of sand.
Shovel: It consists of a steel pan fitted with a long wooden handle. It
is used in mixing, tempering and conditioning the foundry sand by
hand. It is also used for moving and transforming the molding sand to
the container and molding
box or flask.
Fig. Rammers
Fig. Showel
Fig. Sprue Pin
Rammers: Rammers are shown in Fig. These are required for striking the molding sand mass in the
molding box to pack or compact it uniformly all around the pattern.
Sprue pin: It is a tapered rod of wood or iron which is placed or pushed in cope to join mold cavity while
the molding sand in the cope is being rammed.
Trowels: These are used for finishing flat surfaces and comers inside a mould. Common shapes of
trowels are shown as under. They are made of iron with a wooden handle.
Lifter: A lifter is a finishing tool used for repairing the mould and finishing the mould sand. Lifter is also
used for removing loose sand from mould.
Fig. Lifter
Strike off bar: It is a flat bar, made of wood or iron to strike
off the excess sand from the top of a box after ramming.
It’s one edge made beveled and the surface perfectly smooth
and plane.
Vent wire: It is a thin steel rod or wire carrying a pointed edge
at one end and a wooden handle or a bent loop at the other. After
ramming and striking off the excess sand it is used to make small
Fig. Strike off bar
Fig. Vent Wire
Page 33
holes, called vents, in the sand mould to allow the exit of gases and steam during casting.
Slicks: They are also recognized as small double ended mold finishing tool which are generally used for
repairing and finishing the mold surfaces and their edges after withdrawal of the pattern
Fig. Slicks
Swab: Swab is shown in Fig. 11.1(u). It is a small hemp fiber brush used for
moistening the edges of sand mould, which are in contact with the pattern surface
before withdrawing the pattern. It is used for sweeping away the molding sand
from the mold surface and pattern.
Fig. Swab
Gate cutter: Gate cutter (Fig. 11.1(v)) is a small shaped
piece of sheet metal commonly used to cut runners and
feeding gates for connecting sprue hole with the mold cavity.
Fig. Gate Cutter
Bellows: Bellows gun is shown in Fig. 11.1(w). It is hand operated leather made device equipped with
compressed air jet to blow or pump air when operated. It is used to blow away the loose or unwanted sand
from the surfaces of mold cavities.
Draw spike: Draw spike is shown Fig. 11.1(f). It is a tapered steel
rod having a loop or ring at its one end and a sharp point at the
other. It may have screw threads on the end to engage metal
pattern for it withdrawal from the mold.
Sprue Pin: It is a tapered wooden pin, used to make a hole in the
cope through which the molten metal is poured into the mould.
MOULDING BOX:
Moulding box is also called moulding flask. It is frame or box of wood or metal. It is made of two parts
cope and drag as shown in figure.
Page 34
EXP: 01
MOULD FOR A SOLID
Date:
Aim: To prepare a sand mold, using the given single piece pattern.
Raw material required: Moulding sand, Parting sand, facing sand, baking sand, single piece solid
pattern, bottom board, moulding boxes etc.
Tools Required:
1. Molding board
2. Drag and cope boxes
3. Molding sand
4. Parting sand
5. Rammer
6. Strike-off bar
7. Bellows
8. Riser and sprue pins
9. Gate cutter
10. Vent rod
11. Draw spike
12. Wire Brush
1. Sand preparation
2. Placing the mould flask(drag) on the moulding board/ moulding platform
3. Placing the pattern at the centre of the moulding flask
4. Ramming the drag
5. Placing runner and riser
6. Ramming the cope
7. Removal of the pattern, runner, riser
8. Gate cutting
Procedure: Mould Making
1. First a bottom board is placed either on the molding platform or on the floor, making the surface
even.
2. The drag molding flask is kept upside down on the bottom board along with the drag part of the
pattern at the centre of the flask on the board.
3. Dry facing sand is sprinkled over the board and pattern to provide a non-sticky layer.
4. Freshly prepared molding sand of requisite quality is now poured into the drag and on the pattern
to a thickness of 30 to 50 mm.
5. Rest of the drag flask is completely filled with the backup sand and uniformly rammed to compact
the sand.
Page 35
6. After the ramming is over, the excess sand in the flask is completely scraped using a flat bar to the
level of the flask edges.
7. Now with a vent wire which is a wire of 1 to 2 mm diameter with a pointed end, vent holes are in
the drag to the full depth of the flask as well as to the pattern to facilitate the removal of gases
during casting solidification. This completes the preparation of the drag.
8. Now finished drag flask is rolled over to the bottom board exposing the pattern.
9. Using a slick, the edges of sand around the pattern is repaired
10. The cope flask on the top of the drag is located aligning again with the help of the pins of the drag
box.
11. Sprue of the gating system for making the sprue passage is located at a small distance of about 50
mm from the pattern. The sprue base, runners and in-gates are also located as shown risers are
also placed. Freshly prepared facing sand is poured around the pattern.
12. The moulding sand is then poured in the cope box. The sand is adequately rammed, excess sand is
scraped and vent holes are made all over in the cope as in the drag.
13. The sprue and the riser are carefully withdrawn from the flask
14. Later the pouring basin is cut near the top of the sprue.
15. The cope is separated from the drag any loose sand on the cope and drag interface is blown off
with the help of the bellows.
16. Now the cope and the drag pattern halves are withdrawn by using the draw spikes and rapping the
pattern all around to slightly enlarge the mould cavity so that the walls are not spoiled by the
withdrawing pattern.
17. The runners and gates are to be removed or to be cut in the mould carefully without spoiling the
mould.
18. Any excess or loose sand is applied in the runners and mould cavity is blown away using the
bellows.
19. Now the facing paste is applied all over the mould cavity and the runners which would give the
finished casting a good surface finish.
20. A dry sand core is prepared using a core box. After suitable baking, it is placed in the mould
cavity.
21. The cope is placed back on the drag taking care of the alignment of the two by means of the pins.
22. The mould is ready for pouring molten metal. The liquid metal is allowed to cool and become
solid which is the casting desired.
Result: The required mould cavity is prepared using the given Single /solid Pattern.
Page 36
Page 37
EXP: 01
MOULD FOR A Split Pattern.
Aim: To prepare a sand mold, using the given Split-piece pattern.
Raw Material required: Moulding sand, Parting sand, facing sand, baking sand, pattern, bottom board,
moulding boxes.
Tools Required:
1. Molding board
2. Drag and cope boxes
3. Molding sand
4. Parting sand
5. Rammer
6. Strike-off bar
7. Bellows
8. Riser and sprue pins
9. Gate cutter
10. Vent rod
11. Draw spike
12. Wire Brush
1. Sand preparation
2. Placing the mould flask(drag) on the moulding board/ moulding platform
3. Placing the split pattern at the centre of the moulding flask
4. Ramming the drag
5. Placing the pattern at the centre of the moulding flask (Cope box)
6. Placing runner and riser
7. Ramming the cope
8. Removal of the pattern, runner, riser
9. Gate cutting
Procedure: Mould Making
1. First a bottom board is placed either on the molding platform or on the floor, making the surface even.
2. The drag molding flask is kept upside down on the bottom board along with the drag part of the pattern
at the centre of the flask on the board.
3. Dry facing sand is sprinkled over the board and pattern to provide a non-sticky layer.
4. Freshly prepared molding sand of requisite quality is now poured into the drag and on the split-pattern
to a thickness of 30 to 50 mm.
5. Rest of the drag flask is completely filled with the backup sand and uniformly rammed to compact the
sand.
Page 38
6. After the ramming is over, the excess sand in the flask is completely scraped using a flat bar to the
level of the flask edges.
7. Now with a vent wire which is a wire of 1 to 2 mm diameter with a pointed end, vent holes are in the
drag to the full depth of the flask as well as to the pattern to facilitate the removal of gases during
casting solidification. This completes the preparation of the drag.
8. Now finished drag flask is rolled over to the bottom board exposing the pattern.
9. Using a slick, the edges of sand around the pattern is repaired and cope half of the pattern is placed
over the drag pattern, aligning it with the help of dowel pins
10. The cope flask on the top of the drag is located aligning again with the help of the pins of the drag
box.
11. Dry parting sand is sprinkled all over the drag surface and on the pattern
12. Sprue of the gating system for making the sprue passage is located at a small distance of about 50 mm
from the pattern. The sprue base, runners and ingates are also located as shown risers are also placed.
Freshly prepared facing sand is poured around the pattern.
13. The moulding sand is then poured in the cope box. The sand is adequately rammed, excess sand is
scraped and vent holes are made all over in the cope as in the drag.
14. The sprue and the riser are carefully withdrawn from the flask
15. Later the pouring basin is cut near the top of the sprue.
16. The cope is separated from the drag any loose sand on the cope and drag interface is blown off with
the help of the bellows.
17. Now the cope and the drag pattern halves are withdrawn by using the draw spikes and rapping the
pattern all around to slightly enlarge the mould cavity so that the walls are not spoiled by the
withdrawing pattern.
18. The runners and gates are to be removed or to be cut in the mould carefully without spoiling the
mould.
19. Any excess or loose sand is applied in the runners and mould cavity is blown away using the bellows.
20. Now the facing paste is applied all over the mould cavity and the runners which would give the
finished casting a good surface finish.
21. A dry sand core is prepared using a core box. After suitable baking, it is placed in the mould cavity.
22. The cope is placed back on the drag taking care of the alignment of the two by means of the pins.
Page 39
23.
The mould is ready for pouring molten metal. The liquid
metal is allowed to cool and become solid which is the casting
desired.
Result: The required mould cavity is prepared using the given
Split Pattern.
Step :1 Place Drag part of the pattern on mould board and filled
with mould sand
Step -2: Turn drag box upside down and Place cope box over drag box
Step -3: place cope part of the pattern ,riser, Sprue, runner in
position and filled with mould sand.
Placee Drag part of the pattern on Bottom board AND FILLED
WITH MOULD SAND
Step-4: Finally the Mould cavity is produced by removing the
pattern .
Page 40
SHEET METAL WORK
1. INTRODUCTION
Sheet metal work has its own significance in the engineering work. Many products, which fulfill the
household needs, decoration work and various engineering articles, are produced fromsheet metals.
Common examples of sheet metal work are hoopers, canisters, guards, covers, pipes, hoods, funnels,
bends, boxes etc. Such articles are found less expensive, lighter in weight and in some cases sheet metal
products replace the use of castings or forgings.
2. METALS USED IN SHEET METAL WORK:
A metal plate of thickness less than 4 mm is considered as sheet. The size of the sheet is specified by its
length, width and thickness in mm. In British system, the thickness of sheet is specified by a number
called Standard Wire Gauge (SWG). The commonly used gauge numbers and the equivalent thickness in
mm are given below
SWG
16
17
18
19
20
(No.)
Thickness
1.62
1.42
1.22
1.02
0.91
(mm)
The following metals are generally used in sheet metal work:
i.
ii.
iii.
iv.
v.
vi.
vii.
22
24
27
30
0.71
0.56
0.42
0.37
Black Iron Sheet
It is the cheapest among ail. It has a bluish-black appearance and is uncoated sheet. Being
uncoated, it corrodes rapidly. It is prepared by rolling to the desired thickness, then annealed by
pleasing in a furnace and then set aside to cool gradually. The use of this metal is limited to
articles that are to be painted or enameled such as stovepipes, tanks, pans etc.
Galvanized Iron
It is soft steel coated with molten zinc. This coating resist rust, improves appearances, improves
solderability, and improves water resistance. It is popularly known as G.I. sheets. Articles such as
pans, buckets, furnaces, cabinet etc. are made from Gl sheets.
Stainless Steel
It is an alloy of steel with nickel, chromium and traces of other metals. It has good corrosive
resistance. The cost of stainless steel is very high but tougher than Gl sheets. It is used in
kitchenware, food handling equipment, chemical plants etc.
Copper
It is a reddish colored metal and is extremely malleable and ductile. Copper sheets have good
corrosion resistance as well as good appearances but costs are high as compared to Gl and
stainless steel. Because of high thermal conductivity, it is used for the radiator of automobiles,
domestic heating appliances etc.
Aluminium
Aluminium cannot be used in its pure form, but is used in alloy form. Common additions are
copper, silicon, manganese and iron. It has many qualities like high ratio of strength to weight,
corrosion resistant qualities, and ease in fabrication and whitish in color. It is used in
manufacturing of a number of products such as refrigerator trays, household appliances, lighting
fixtures, window work, construction of airplanes and in many electrical and transportation
industries.
Tin Plates
It is an iron sheet coated with the tin to protect it against rust. This metal has a very bright silvery
appearance and is used principally in making food containers, cans and pans.
Lead
It is a very soft, malleable, low melting point and possesses high resistance to acid corrosion. It is
having low mechanical strength so it is used to provide lining to the highly corrosive acid tanks. It
is also used in radiation shielding.
Page 41
3. HAND TOOLS:
For measuring, marking cutting and forming, various types of hand tools are used in sheet metal work. A
list of them is given below:
I.
Measuring tools
II.
Marking tools
III.
Cutting tools
IV.
Forming tools
V.
Joining tools
I. MEASURING TOOLS
The following types of tools are commonly used in sheet metal
shops to measure the dimensions of work pieces:
1. Steel rule
2. Vernier caliper
3. Micrometer
4. Sheet Metal gauge
The above tools are already explained in the fitting section.
SHEET METAL GAUGE
It is a disc shaped piece of metal, having a number of slots on the
outside edge as shown in figure. The slots are of various widths
and each corresponds to a certain standard wire gauge (SWG)
number. The gauge is placed over the edge of the sheet to
be measured and a slot is found that will slip over the metal
with a light fit pressure. Standard tables are referred to for
Fig . Standard wire gauge
Fig . Scriber
conversion of SWG numbers to mm sizes.
II. MARKING TOOLS:
1. Scriber:It is used to scribe or mark line on a metal surface for
a variety of purposes. It is a metalworker's pencil
2. Trammel: These are used for drawing large circles and arcs
that are beyond the limit of dividers. It has two straight,
removable legs tapered to a needle point mounted on separate
holders which slide on steel (or wooden) bar and held in position
by thumb screws.
Fig . Trammel Points
3. Punches: It is used in sheet metal work for marking on sheet, locating centers. There are two types of
punches. a) Dot punch and b) Prick punch.
These are already explained in fitting section in detail.
III CUTTING TOOLS:
To cut the sheet metal as per the pattern drawn and to
make holes for rivets etc., the following types of tools
are used.
A snip is a hand shear used to cut thin sheets of gauge
size number 20 or above. It works like ordinary
scissors. There are several types and sizes of snips
available to cut along straight lines or curved lines.
Figure (a) shows a straight snip having straight blades to cut along straight lines. Figure (b) shows a bent
Page 42
snip having curved blades to cut along curved lines. These snips are used for cutting thin sheets. The
heavier types are known as bench shear and block shear.
Fig. Mechanical Shearing press
IV. FORMING TOOLS:
Shaping of the sheet metal such as folding, bending, curling, etc., are done by using the following types of
forming tools.
1. Stakes:
Stakes are the sheet metal anvils used for bending, seaming and forming by using ahammer or mallet.
They work as the supporting tool as well as the forming tools. They are madein different sizes and shapes
depending upon the job requirement. Commonly used stakes are
Stake Holder
The stake holder used in sheet metal shop is a rectangular bench plate as shown in Figure.
Page 43
Fig. Stake Holder
2. HAMMERS:
The sheet metal is shaped by hammering or striking with mallet, after keeping the work on suitable form
of stake. The hammers used for sheet metal work are (a) Setting hammer, for setting down the edge while
making double seam, (b) Raising hammer for forming curved or hollow shape from flat piece, and (c)
Riveting hammer for riveting purpose. Mallets are soft hammers used to give soft blows which will not
damage the sheet at the same time will shape them. The commonly used types of hammers and mallets are
shown in Figure.
IV JOINING TOOLS:
The tools exclusively used for making and finishing joints are:
a) Hand grooves b) Rivet set c) Soldering irons
Hand groovers: Hand groovers are used to flatten and shape joints made in sheet
metal. The tool has a groove of required width and depth like a die. This groover is
placed over the joint (double hem or lock seam) and hammered from the top of it, to
shape the joint that of the groove as shown figure.
RIVET SET:
Rivet get is made of tool steel. At
the bottom of the rivet set there is a
deep hole and a cup-shaped hole.
Fig. Rivet set
The deep hole is used to draw a rivet
through sheet metal and cup shaped hole is
used to form the finished head of the rivet- Another hole on the aide of
the set is to release the burrs that are punched. Dollies are used to backup
rivets, when it is not possible to support the job on a bench.
Fig. Rivet set and dolly
SOLDERING IRON:
Fig. handle.
Rivet setItand
dolly in
A soldering iron consists of a copper block, fixed on an iron rod with a wooden
is made
various shapes and sizes to suit the use as shown in figure. The purpose of the copper block is to act as a
Page 44
heat source for melting and spreading the solder (filler metal) at the joining area. The soldering iron
(copper) is heated using furnace, blower or by electrical resistance.
Fig. Soldering Iron
SHEET METAL JOINTS:
The line of joint on a sheet me ml pieces is called seam. The most common types of seams are as follows:
1. Lap seam: This is the simplest seam used in sheet metal work (Figure (a)). This consists of one
edge lapping over the other and joint is made by soldering or riveting.
2. Grooved seam: A grooved seam is made by hooking two-folded edges together and then off
setting them as shown in Figure 5.8(b). This joint is self-locking and stronger to some extent than
lap seam.
3. Single seam: This seam is used to join a bottom portion to a vertical body as shown in Figure (c).
The bottom edge is hooked over the bent edge of the vertical body. This method of joint can be
used for square, rectangular or round containers.
4. Double seam: This seam is similar lo single scam with the difference that the formed edge is bent
upwards against the body as shown in Figure (d).
5. Dove-tail seam: This seam is used to connect a cylindrical piece to a flat as shown in Figure (e).
The edge of the cylindrical part to be joined is slit at short distance and is bent so that alternate
pieces come inside and outside of the joint. Permanent joint is obtained by soldering or riveting.
6. Flanged (burred) bottom seam: This seam is used to fasten the bottom of a container to its
body. The flange of a cylindrical job is often called a burr. The joint consists of a narrow flange
which may be joined to inside or outside of the vessel as shown in figure (f).
Edge Forming
For sheet metal objects strength is given to the edge and the sharpness is eliminated by folding the edge.
The common types of folding used in sheet metal work are as follows:
1. Single hem 2. Double hem 3. Wired edge
Figure shows the three types of edge folding. A wired edge consists of an edge wrapped around a steel
wire for better strength.
Page 45
Page 46
EXP: 01
RECTANGULAR TRAY
AIM: To make a rectangular Tray as per required dimensions.
MATERIALS REQUIRED:
Galvanized Iron sheet (150*110*26 gauge)
1. Steel rule
2. Flat file
3. Scriber
4. Try square
5. Snips
6. Dot punch
7. Stakes
8. Mallet
OPERATIONS TO BE
CARRIED OUT:
1. Planning
2. Marking
3. Cutting
4. Bending
5. Seaming
6. Soldering
PROCEDURE:
1. The size of the given sheet is checked with steel rule.
2. Mark the measurement and make the development surface sketch diagram.
3. The layout of the tray is marked on given sheet.
4. The layout of the tray is cut by using the straight snips.
5. The sheet is bent to the required shape using stakes and mallet.
6. Now the bent edges are made to overlap each other and stuck with a mallet to get the required joint.
7. The joint is soldered.
PRECAUTIONS:
1. Care should be taken while cutting with snip.
2. Care should be taken while bending and jumping.
RESULT:
The rectangular tray is done success fully made
Page 47
EXPT NO: 02
ROUND PIPE
AIM: To make a cylindrical pipe as per required dimensions.
MATERIALS REQUIRED:
Galvanized Iron sheet (100*38*26 gauge)
1. Steel rule
2. Flat file
3. Scriber
4. Try square
5. Snips
6. Dot punch
7. Stakes
8. Mallet
OPERATIONS TO BE
CARRIED OUT:
1. Planning
2. Marking
3. Cutting
4. Bending
5. Seaming
6. Soldering
PROCEDURE:
1. The size of the given sheet is checked with steel rule.
2. Mark the measurement and make the development surface sketch diagram.
3. The layout of the cylindrical shape pipe is marked on the given sheet.
4. The sheet is bent to the required shape using stakes and mallet.
5. Now the edges are slightly bent to one is one side and the other is opposite side, using stakes and
mallet.
6. Join both the ends with in a cylindrical shape.
PRECAUTIONS:
1. Care must be taken while cutting snips.
2. Care must be taken while bending and joining.
RESULT:
The cylindrical shape is made successfully.
Page 48
WELDING
Welding is a process for joining two similar or dissimilar metals by fusion. It joins different metals/alloys,
with or without the application of pressure and with or without the use of filler metal. The fusion of metal
takes place by means of heat. The heat may be generated either from combustion of gases, electric arc,
electric resistance or by chemical reaction.
Welding provides a permanent joint but it normally affects the metallurgy of the components. It is
therefore usually accompanied by post weld heat treatment for most of the critical components. The
welding is widely used as a fabrication and repairing process in industries. Some of the typical
applications of welding include the fabrication of ships, pressure vessels, automobile bodies, off-shore
platform, bridges, welded pipes, sealing of nuclear fuel and explosives, etc.
Most of the metals and alloys can be welded by one
type of welding process or the other. However,
some are easier to weld than others. To compare
this ease in welding term ‘weldability’ is often
used. The weldability may be defined as property
of a metal which indicates the ease with which it
can be welded with other similar or dissimilar
metals.
Terminology of welding process
Elements of welding process used with common
welding joints such as base metal, fusion zone, weld face, root face, root opening toe and root are depicted
in Figure.
Edge preparations
For welding the edges of joining surfaces of metals are prepared first. Different edge preparations may be
used for welding butt joints, which are given in Figure.
Welding joints
Some common welding joints are shown in Figure. Welding joints are of generally of two major kinds
namely lap joint and butt joint. The main types are described as under.
Page 49
1. Lap weld joint
Single-Lap Joint
This joint, made by overlapping the edges of the plate, is
not recommended for most work. The single lap has very
little resistance to bending. It can be used satisfactorily for
joining two cylinders that fit inside one another.
Double-Lap Joint
This is stronger than the single-lap joint but has the
disadvantage that it requires twice as much welding.
Tee Fillet Weld
This type of joint, although widely used, should not be employed if an alternative design is possible.
2. Butt weld joint
a. Single-Vee Butt Weld
It is used for plates up to 15.8 mm thick. The angle of the vee depends upon the technique being used,
the plates being spaced approximately 3.2 mm.
b. Double-Vee Butt Weld
It is used for plates over 13 mm thick when the welding can be performed on both sides of the plate.
The top vee angle is either 60° or 80°, while the bottom angle is 80°, depending on the technique
being used.
Welding Positions
As shown in Fig. 17.4, there are four types of welding positions, which are given as:
a. Flat or down hand position
b. Horizontal
position
c. Vertical
position
d. Overhead
position
Flat or Down-hand Welding Position
The flat position or down hand position is one in which the welding is performed from the upper side of
the joint and the face of the weld is approximately horizontal.
Horizontal Welding Position
In horizontal position, the plane of the workpiece is vertical and the deposited weld head is horizontal.
This position of welding is most commonly used in welding vessels and reservoirs.
Vertical Welding Position
In vertical position, the plane of the work-piece is vertical and the weld is deposited upon a vertical
surface. It is difficult to produce satisfactory welds in this position due to the effect of the force of gravity
on the molten metal.
Overhead Welding Position
Page 50
The overhead position is probably even more difficult to weld than the vertical position. Here the pull of
gravity against the molten metal is much greater.
ARC WELDING PROCESSES
The process, in which an electric arc between an
electrode and a work-piece or between two
electrodes is utilized to weld base metals, is called
an arc welding process. The basic principle of arc
welding is shown in Figure1. However the basic
elements involved in arc welding process are
shown in Figure2. Most of these processes use
some shielding gas while others employ coatings or
fluxes to prevent the weld pool from the
surrounding atmosphere.
1)
2)
3)
4)
5)
Switch box.
Secondary terminals
Welding machine.
Current reading scale.
Current regulating hand
wheel.
6) Leather apron.
7) Asbestos hand gloves.
8) Protective glasses strap
9) Electrode holder.
10) Hand shield
Fig1.The basic principle of arc welding
11) Channel for cable
protection.
12) Welding cable.
13) Chipping hammer.
14) Wire brush.
15) Earth clamp.
16) Welding
table
(metallic).
17) Job.
Fig2.The basic elements of arc welding
Arc Welding Equipment
Arc welding equipment, setup and related tools and accessories are shown in Figure. However some
common tools of arc welding are shown separately through Figure. Few of the important components of
arc welding setup are described as under.
1. Arc welding power source
Both direct current (DC) and alternating current (AC) are used for electric arc welding, each having its
particular applications. DC welding supply is usually obtained from generators driven by electric motor
or if no electricity is available by internal combustion engines. For AC welding supply, transformers are
predominantly used for almost all Arc-welding where mains electricity supply is available. They have to
step down the usual supply voltage (200-400 volts) to the normal open circuit welding voltage (50-90
volts). The following factors influence the selection of a power source:
a. Type of electrodes to be used and metals to be welded
b. Available power source (AC or DC)
c. Required output
d. Duty cycle
e. Efficiency
f. Initial costs and running costs
g. Available floor space
h. Versatility of equipment
2. Welding cables
Page 51
Welding cables are required for conduction of current from the power source through the electrode
holder, the arc, the work piece and back to the welding power source. These are insulated copper or
aluminum cables.
3. Electrode holder
Electrode holder is used for holding the electrode manually and
conducting current to it. These are usually matched to the size of the
lead, which in turn matched to the amperage output of the arc welder.
Electrode holders are available in sizes that range from 150 to 500
Amps.
Fig. Electrode Holder
4. Welding Electrodes
An electrode is a piece of wire or a rod of a metal or
alloy, with or without coatings. An arc is set up
between electrode and workpiece. Welding
electrodes are classified into following types(i) Consumable Electrodes
(a) Bare Electrodes
(b) Coated Electrodes
(ii) Non-consumable Electrodes
(a) Carbon or Graphite Electrodes
(b) Tungsten Electrodes
Fig. Parts of a electrode
Consumable electrode is made of different metals and their alloys. The end of this electrode starts
melting when arc is struck between the electrode and workpiece. Thus consumable electrode itself acts
as a filler metal. Bare electrodes consist of a metal or alloy wire without any flux coating on them.
Coated electrodes have flux coating which starts melting as soon as an electric arc is struck. This
coating on melting performs many functions like prevention of joint from atmospheric contamination,
arc stabilizers etc.
Non-consumable electrodes are made up of high melting point materials like carbon, pure tungsten or
alloy tungsten etc. These electrodes do not melt away during welding. But practically, the electrode
length goes on decreasing with the passage of time, because of oxidation and vaporization of the
electrode material during welding. The materials of non-consumable electrodes are usually copper
coated carbon or graphite, pure tungsten, thoriated or zirconiated tungsten.
5. Hand Screen
Hand screen used for protection of eyes and supervision of weld bead.
6. Chipping hammer
Chipping Hammer is used to remove the slag by striking.
7. Wire brush
Wire brush is used to clean the surface to be weld.
52
Fig. Earth Clamp
Fig. Chipping Hammer
Fig. Wire Brush
8. Protective clothing
Operator wears the protective clothing such as apron to keep away the exposure of direct heat to the
body.
Safety Recommendations for ARC Welding
The beginner in the field of arc welding must go through and become familiar with these general safety
recommendations which are given as under.
1. The body or the frame of the welding machine shall be efficiently earthed. Pipe lines containing
gases or inflammable liquids or conduits carrying electrical conductors shall not be used for a
ground return circuit All earth connections shall be mechanically strong and electrically adequate
for the required current.
2. Welding arc in addition to being very is a source of infra-red and ultra-violet light also;
consequently the operator must use either helmet or a hand-shield fitted with a special filter glass to
protect eyes
3. Excess ultra-violet light can cause an effect similar to sunburn on the skin of the welder
4. The welder’s body and clothing are protected from radiation and burns caused by sparks and flying
globules of molten metal with the help of the following:
5. Gloves protect the hands of a welder.
6. Leather or asbestos apron is very useful to protect welder’s clothes and his trunk and thighs while
seated he is doing welding.
7. For overhead welding, some form of protection for the head is required
8. Leather skull cap or peaked cap will do the needful.
9. Leather jackets and 1ather leggings are also available as clothes for body protection.
10. Welding equipment shall be inspected periodically and maintained in safe working order at all
times.
11. Arc welding machines should be of suitable quality.
12. All parts of welding set shall be suitably enclosed and protected to meet the usual service
conditions.
53
EXPT NO: 01
BUTT JOINT
Aim: To make a Butt joint using the given two M.S pieces by arc welding.
Material Required:
Mild steel plate of size 100X50X5 mm – 2 No’s
Welding Electrodes: M.S electrodes 3.1 mm X350 mm
Welding Equipment: Air cooled transformer
Voltage-80 to 600 V 3 phase supply, amps up to 350
Tools and Accessories required:
1. Rough and smooth files.
2. Protractor
3. Arc welding machine (transformer type)
4. Mild steel electrode and electrode holder
5. Ground clamp
6. Tongs
7. Face shield
8. Apron
9. Chipping hammer.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Marking
Cutting
Edge preparation (Removal of rust, scale etc.) by filling
Try square leveling
Tacking
Welding
Cooling
Chipping
Cleaning
Procedure:
1. The given M.S pieces are thoroughly cleaned of rust and scale.
2. One edge of each piece is believed, to an angle of 300, leaving nearly ¼ th of the flat thickness,
at one end.
3. The two pieces are positioned on the welding table such that, they are separated slightly for
better penetration of the weld.
4. The electrode is fitted in the electrode holder and the welding current is ser to be a proper value.
5. The ground clamp is fastened to the welding table.
6. Wearing the apron and using the face shield, the arc is struck and holding the two pieces
together; first run of the weld is done to fill the root gap.
7. Second run of the weld is done with proper weaving and with uniform movement. During the
process of welding, the electrode is kept at 150 to 250 from vertical and in the direction of
welding.
8. The scale formation on the welds is removed by using the chipping hammer.
9. Filling is done to remove any spanner around the weld.
54
DRAWING:
Result:
The single V-butt joint is thus made, using the tools and equipment as mentioned above.
55
EXPT NO: 02
LAP JOINT
Aim: To make a Lap joint, using the given two M.S pieces and by arc welding.
Material Supplied:
Voltage-80 to 600 V,3-ɸ supply, Current up to 350Amps
2. Protractor
5. Ground clamp
6. Tongs
7. Face shield
8. Apron
9. Chipping hammer.
1. Marking
2. Cutting
3. Edge preparation (Removal of rust, scale etc.) by filling
4. Try square leveling
5. Tacking
6. Welding
7. Cooling
8. Chipping
9. Cleaning
Procedure:
2. The two pieces are positioned on the welding table such that, the two pieces overlapped one
over the other as shown in drawing.
5. Wearing the apron and using the face shield, the arc is struck and the work pieces are tackwelded at both the ends and at the centre of the joint.
6. The alignment of the lap joint is checked and the tack-welded pieces are required.
DRAWING:
56
Result:
The Lap joint is thus made, using the tools and equipment as mentioned
57
EXPT NO: 03
CORNER JOINT
Aim: To make a corner joint, using the given two M.S pieces and by arc welding.
Material Supplied:
Voltage-80 to 600 V 3 phase supply, amps up to 350
2. Protractor
5. Ground clamp
6. Tongs
7. Face shield
8. Apron
9. Chipping hammer.
1. Marking
2. Cutting
3. Edge preparation (Removal of rust, scale etc.) by filling
4. Try square leveling
5. Tacking
6. Welding
7. Cooling
8. Chipping
9. Cleaning
Procedure:
2. The two pieces are positioned on the welding table such that, the L shape is formed. The tongs
are made use of for the purpose.
5. Wearing the apron and using the face shield, the arc is struck and the work pieces are tackwelded at both the ends and at the centre of the joint.
6. The alignment of the corner joint is checked and the tack-welded pieces are required.
58
Result: The corner joint is thus made, using the tools and equipment as mentioned
59
HOUSE WIRING
INTRODUCTION:
Power is supplied to domesticate installations through a phase and neutral, forming a single phase AC
230 v to wire system. For individual establishment power is supplied through three phase two wire
system. To give 440V, the neutral is earthed at to the domestic utilities; power is fed to kilo watt meter
and then to distributes power along several circuits. It also protects these circuits from over load by
safety devices like fuses or circuit breakers.
ELEMENTS OF HOUSE WIRING:
1.
2.
3.
4.
5.
6.
7.
Fuses and circuit breakers
Electric switch
Plug
Socket out let
Lamp holder
Main switch
Incandesant tight
WIRING METHOD: A circuit is path along which the electric current flows from negative side of
power source to positive side.
COMMON HOUSE WIRING REPAIRS:
1.
2.
3.
4.
Replacing a fuse
Resulting a circuit beaker
Resulting a switch or an out let
Repair of house hold appliances
PRECAUTIONS:
1. Ensure that the insulation of wire reaches up to accessory
2. Do not over tighten the screw
3. Ensure that the base wire is not touching any part of accessory.
RULERS OF WIRING:
1. Every fitting or appliances must also be controlled by a switch.
60
2. The switch should be on the line conductor
3. Every sub-circuit must have a separate fuse.
All the metals covering frames etc. should be earthed.
Incandescent Light:
In candescent means ‘glowingat white hot’ .A lamp actually work slike aheating
element,exceptthat it gives of flight by becoming whiteh ot. Figure3.9. shows the part s of a bulb. The
amount of powerit consume sisstamped on the bulb. The higher the wattage, brighterthe light.The bulbs
have filaments made of tungsten. However, special bulbs are available with inside coating and filled with
gas.
Wires and Wire Sizes:
A wire is defined asa bare or an insulated conductor consisting of one or several strands. An
insulated wire consists of a conductor with insulating material made of vulcanized India rubber (VIR) or
polyvinylchloride (PVC). The wire may consist o f one or several twisted strands. A multi core
conductor consists of several cores insulated from one another and enclosed in a common sheathing
(fig.3.10).
Wires ize sare specified by diameter of the wire, using a stand ard wire gauge (SWG), which
also gives an ideao f the current carrying capacity. Thespecification consist so fb ot htheno. Of
strandsand the diameter of each wire in it. Forexample, the specification, (i)silk wire14/36
indicates14strands of 36SWG each and
(ii )3/18 PVC indicates 3 strands of 18SWG each.
61
EXPT NO: 1
DATE:
ONE LAMP CONTROLLED BY ONE SWITCH
AIM: To control one lamp by a one switch with provision for plug socket with switch control.
MATERIALS REQUIRED WITH DIMENSIONS:
1. 1/18”pvc wire of sufficient length
2. One way switch – 2 no.
3. Two-pin plug socket-1no.
4. Bulb-1no.
5. Bulb holder-1no.
1. 6”cutting pliers
2. 1.5 IB ball peen hammer.
3. Wire stripper
4. Tester
5. 6”screw drivers
6. Hack saw
7. 12mm hand drilling machine.
OPERATIONS TO BE CARRIED OUT:
1. Fitting the wires
2. Connection of the bulb holder
3. Connection of plug socket
4. Connection of switch
5. Circuit connections
6. Power from mains
7. Operation the bulb
8. Testing the plug socket.
PROCEDURE:
1. The outline wiring diagram marked on the wooden board and clips are nailed to the board
following the diagram, six wire pieces are taken and insulation is removed at the ends by using
wire stripper.
2. A phase wire is connected to one point switch s1 and s2.
3. The lower points of switches s1ands2 are connected to one point of bulb holder and one point of
plug socket respectively.
4. Two neutral wires are taken and one in connected to the remaining point of the bulb holder.
5. The other is connected to the remaining points of plug socket.
6. After checking the proper circuit connections the power supply is given.
7. Now the bulb is ready to glow bright and the plug socket is also ready with control.
PRECAUTIONS:
1. All the wire connections of the switches, bulb holder and sockets are tight.
2. Too many load connections fr4om a single junction are avoided.
RESULT:
When the wires are connected the bulb glows.
62
EXPT NO:2
DATE:
TWO LAMPS CONTROLLED BY SINGLE SWITCH
AIM: to control two lamps by a one switch with provision for plug socket with switch control.
MATERIALS REQUIRED WITH DIMENSIONS:
1. 1/18”pvc wire of sufficient length
2. One way switch – 2 no.
3. Two-pin plug socket-1no.
4. Bulb-1no.
5. Bulb holder-1no.
1. 6”cutting pliers
2. 1.5 IB ball peen hammer.
3. Wire stripper
4. Tester
5. 6”screw drivers
6. Hack saw
7. 12mm hand drilling machine.
OPERATIONS TO BE CARRIED
OUT:
3. Connection of plug socket
4. Connection of switch
5. Circuit connections
6. Power from mains
7. Operation the bulb
8. Testing the plug socket.
PROCEDURE:
1. The outline wiring diagram marked on the wooden board and clips are nailed to the board
following the diagram, six wire pieces are taken and insulation is removed at the ends by using
wire stripper.
2. A phase wire is connected to one point switch s1 and s2.
3. The lower points of switches s1ands2 are connected to one point of bulb holder and one point of
plug socket respectively.
4. Two neutral wires are taken and one in connected to the remaining point of the bulb holder.
5. The other is connected to the remaining points of plug socket.
6. After checking the proper circuit connections the power supply is given.
7. Now the bulb is ready to glow bright and the plug socket is also ready with control.
PRECAUTIONS:
1. All the wire connections of the switches, bulb holder and sockets be tight.
2. Too many load connections fr4om a single junction are avoided.
RESULT:
1. In series connection if one bulb does not glow the bulb also does not glows.
2. In parallel connection if one bulb does not glow the other bulb blows.
63
EXPT NO: 3
DATE:
STAIR CASE WIRING
Aim: To do stair case wiring (i.e. control of one lamp by two switches fixed at two
different places).
Materials required:
PVC wire of sufficient length 5-no,Two-way
switches, bulb holders, ceiling rose and bulb.
Tools and equipment used:
1. 6’’ cutting pliers,
2. 6’’screwdrivers,
3. Wire stripper
4. Tester
.Operations to be carried out:
3. Connection of switches
4. Circuit-connection
5. Power from mains
6. Operating the lamp
Procedure:
A phase wire is taken and its one end is connected to the middle point of two – way
switch, S1. While the other end is connected to the phase point of main supply. Another phase
wire (second wire) is taken and used for connecting the lower points of the two switchesS1;
S2.The third phase wire piece is taken and is connected between the middle point of S2 and
one of the points o f the bulb holder .A neutral wire piece is taken and its one end is connected
to the remaining points of bulb holders, while the other end is connected to main supply. Now
the glowing of the bulb is controlled by two way switches.
Precautions:
1. All wire connections to the switches and bulb holders should be right.
2. Always red wire should be used for phase and black for neutral.
3. Too many load connections from a single junctions are avoided
4. Switch should be connected in phase only.
Result and conclusion:
Stair case wiring (i.e. control of one lamp by two switches fixed at two different
places) is done.
S.No.
1
2
3
4
EXPT NO: 4
DATE:
S1
Up
Up
Down
Down
S2
Up
Down
Up
Down
Lamp
Bright
Off
Off
Bright
CONTROLLING TWO LAMPS BY TWO INDEPENDENT SWITCHES
64
Aim: To control two lamps by two independent switches located at two different places.
Materials required:1/18’’PVC wire of sufficient length 5-no, two way switches, bulb holders, ceiling
rose and bulbs.
3. 1.5 lb ball-peen hammer
4. Hacksaw
5. Wire stripper
6. 12mmhanddrillingmachine
7. Tester
. .Operations to be carried out:
3. Connection of switches
4. Circuit-connection
5. Power from mains
6. Operating the lamp
Procedure:
Five phase wire pieces are taken and insulation is removed at the ends by wire stripper.
The first phase wire is connected by seconds phase wire. The middle point of switchesS2 is
connected to one point of bulb holder “B2”. By using another phase wire the remaining point
o f the bulbholder“B1”. At the same point of bulb“B1” a phase wire connected to the upper
point of switch“S1”. Two neutral wire pieces are taken and connected to the remaining point
of bulbholder“B1”. One of it is connected to the main supply. After checking the proper
circuit connects the power supply is given to switches. Now the bulbs are ready to show
bright and dim.
Precautions:
1.
2.
3.
4.
All wire connections to the switches and bulb holders should be right.
Always red wire should be used for phase and black for neutral.
Too many load connections from a single junctions are avoided
Switch should be connected in phase only.
Result:
Controlling of two lamps by two independent switches located at two different places is done.
S. No
EXPT NO: 5
S1
S2
L1
L2
1
UP
DOWN BRIGHT OFF
2
UP
UP
3
DOWN UP
OFF
OFF
4
DOWN DOWN DIM
DIM
BRIGHT BRIGHT
FLUORESCENT LAMP WIRING
Aim: To prepare the “Fluorescent Lamp”.
65
DATE:
Materials required:
1/18’’PVC wire of sufficient length 5-no, one-wayswitch-1, starter-1, choke-1, fluorescent lamp, holders
with frame.
6’’ cutting pliers, 6’’screwdrivers, 1.5 lb ball-peen hammer, Hacksaw, Wire stripper, 12mm hand
drilling machine, Tester
Operations to be carried out:
Fitting the wires
Connection of the fluorescent lamp
Connection to choke
Connection of switches
Circuit-connection
Power from mains
Operating the lamp
Procedure:
6’’PVC wire pieces are taken and insulation is removed at the ends by using wire stripper. A
phase wire is connected to one point on the switch. The other point of the switch is connected to
Choke. The other point of the Choke is connected to one point of the starter and the other point of
l amp holder-1. The other point of the lamp holder-1 is connected to one point of the Starter. A
neutral wire pieces taken and connected to one point of the lampholder-2. The other point of the
lamp holder-2 is connected to Remaining point of the Starter. After checking proper circuit
connections the power supply is given. Now the lamp is ready to glow.
Precautions:
1.
2.
3.
4.
All wire connections to the switches and bulb holders should be tight.
The switches must be in off position before giving power supply
Result: Operating the fluorescent lamp is done.
EXPT NO: 6
GODOWN WIRIN
DATE:
Aim: To prepare a Godown wiring circuit with PVC conduit wiring system.
Materials required:
PVCwireofsufficientlength5-no, Two-way switches, bulb holders, ceiling rose and bulb,
66
7. Wire stripper
8. 12mmhanddrillingmachine
9. Tester
Operations to be carried out:
1.
2.
3.
4.
5.
6.
Procedure:
Fitting the wires
Connection of the bulb holder
Connection of switches
Circuit-connection
Power from mains
Operating the lamp
A phase wire is taken and its one end is connected to the middle point of two – way
switch, S1. While the other end is connected to the phase point of main supply. Another phase
wire (second wire) is taken and used for connecting the upper points of the two switches S1
with middle point of switch S2..The third phase wire piece is taken and is connected between
the upper point of S2 and one of the points of the bulb holder .A neutral wire piece is taken
and its one end is connected to the remaining points of bulb holders, while the other end is
connected to main supply. Now the glowing of the bulb is controlled by two way switches.
Precautions:
5.
6.
7.
8.
All wire connections to the switches and bulb holders should be right.
Too many load connections from a single junctions are avoided
Result and conclusion:
GD wiring is done.
67
PLUMBING
Plumbing is a skilled trade of working with pipes or tubes and plumbing fixtures. The process
is mainly used for the supply of drinking water and the drainage of waste water, sometimes mixed with
waste floating materials in a living or working place. A plumber is someone who installs or repairs
piping systems, plumbing fixtures and equipment such as valves, washbasins, water heaters, water
closests, etc. Thus it usually refers to a system of pipes and fixtures installed in a building for the
distribution of water and the removal of waterborne wastes.
The latin word plumbum, means metal lead pipe, is the origin for developing the term
plumbing. Plumbing process was originated during the ancient civilizations such as the greek, Roman,
Persian, Indian and Chinese civilizations as they developed public baths and needed to provide potable
water, and drainage of wastes carried by water.
PIPES AND THEIR JOINTS:
Pipes are manufactured by using different types of materials like steel, cast iron, galvanized
iron, brass, copper, aluminum, lead, plastic, concrete, asbestos, etc. They are usually classified
according to the material. They are also grouped as cast, welded, seamless, extruded, etc. For conveying
large quantity of water, cast iron, steel or concrete pipes having large diameter are usually used.
Galvanized iron pipes (GI pipes) are popular for medium and low pressure water supply lines.
Plastic pipes are preferred for household uses at low pressure. Pipes are generally specified by
their inner diameter (Nominal diameter specified in inches). Hence, the pipe fitting size is also based on
this dimension. But for plastic pipes, this rule is not strictly followed because threading is not usually
required for them. For engineering uses, along with the nominal diameter, the pipe thickness is also
specified as light, medium or heavy.
Types of pipe joints:
According to the pipe material, size and application, different methods are used to join pipes. The most
common types of pipe joints are:
1.
2.
3.
4.
5.
Screwed pipe joint – For GI Pipes
Welded pipe joint – for steel, copper, aluminum and lead pipes
Flanged pipe joint – for cast iron and steel pipes
Soldered pipe joint – for brass and copper tubes
Glued or cemented pipe joint – for PVC pipes
Pipes made of iron (GI Pipes) and brass of small and medium diameters (10 mm to 100 mm) are usually
joined by screwing the pipe specials with internal or external threads. Welding is used to make
permanent joint of medium and large diameter steel pipes. Flanged pipe joints are common in medium
and large diameter pipes of cast iron and steel, along with rubber/CAF (Compressed asbestos fibre)
gaskets. The flanged are screwed to the pipe for smaller diameter but made integral for large diameters.
Pipes of copper and brass are usually joined by soldering.
PVC (poly Vinyl Chloride) pipe is the most popular choice in plastic group. It is rigid and uses thread
and solvent weld (glue) connections. It also can be heat fused. PVC pipes are available in various
pressure ratings for water supply, and is a very choice for landscape irrigation. The reasons for the
popularity are the economy, no corrosion and easiness to work. CPVC is a different type of plastic,
which has an extra chlorine atom in the compound, can be used for the hot water supply, and in
industry.
To join plastic pipes, gluing or cementing method is used. Solvent cement is the gluing material and it
partially melts the surface of the plastic pipe to make the joint. As the glue evaporates within two
minutes, a strong joint is obtained.
68
Screwed pipe fittings, (pipe specials) are removable or temporary pipe connections which permit
necessary dismantling or reassembly for the purpose of installation, maintenance, cleaning, repair, etc.
The functions of pipe fittings can be broadly classified as:
1. To join two or more pipe lines together
2. To effect change in diameter or direction
3. To close the end of a pipe line
The most common types of screwed pipe fittings used in galvanized iron (GI) pipe lines and plastic
(PVC) pipe lines are shown in Figure 1 (I to 17). A brief description of these fittings is given below
1. Coupler (coupling): Two pipe lines of equal diameter and in axial alignment can be joined by a
coupler (coupling). It is a short sleeve with internal thread.
2. Reducer coupler (Reducer coupling): This is a coupler to join two pipe lines of different diameters
in axial alignment.
3. 900 Elbow: This is a pipe special used or effecting abrupt change in direction through 90°. Internal
threads are provided on both ends. An elbow brings twice the head loss than a bend.
4. 900 Reducer elbow: This is an elbow with outlet diameter less than that of inlet diameter It is used to
join two pipe lines having different diameters and meeting at right angle.
5.Bend: This is a pipe special used to effect gradual change in direction (usually 90°).The two ends of
the bend are externally threaded.
6. Return hand: This bend is used to return the direction of pipe line through 180°.The ends are
internally threaded for fitting the pipe lines.
1. Tee: This pipe special is used to make a branch connection of same diameter to the main pipe line at
right angle. A Tee is internally threaded and it connects three ends of pipes.
8. Reducer Tee: This is a pipe special similar to Tee used to take a branch connection of reduced
diameter from the main pipe line.
9, Cross: This pipe special is used to take two branch connections at right angles to the main pipe line.
The threads are provided internally,
10. Close nipple: A nipple is a short straight piece of pipe with external thread on both ends. A close
nipple is the shortest one of this category with external thread for the full length. They are used to join
two internally threaded pipe specials and valves.
11. Short nipple: A short nipple has the same shape and function of a close nipple, but it has a short
unthreaded portion at the middle of its length for gripping.
12. Short nipple with hexagonal grip: This nipple has an additional hexagonal nut shape at the middle
portion for easy screwing with spanner. It is similar to an ordinary short nipple, except that difference.
13. Hose nipple: A hose nipple is used to connect a hose (flexible pipe-usually plastic or rubber) to a
pipe line. One end of the hose-nipple has a stepped taper to fit the hose, while other end has thread. A
hexagonal nut shape is given to the middle portion for gripping with a spanner.
14. Male plug: A male plug is used to close an internally threaded end of a pipe line or pipe special. It
has external thread and a grip of square shape at the end.
15. Female plug (cap): A female plug is used to close an externally thread end of a pipe or pipe special.
It has internal thread and a grip of square shape at the end.
16. Screwed union: II consists of three pieces as shown in the drawing. The two end pieces have
internal threads at their ends which are connected to the pipe ends. The central hexagonal (or octagonal)
piece (union nut) has internal thread at one end and a collar at the other end. After the end pieces are
screwed on to the pipes, the central piece (union nut) is tightened to draw the end pieces together to get
a water tight joint.
17. Flange: This is a disc type pipe special having threaded hole at the centre for screwing to the
externally threaded end of a pipe line. It will have holes around the central hole at equal angular spacing
(3, 4, 6f or 8 Nos.) for joining to another similar flange or flat surface using bolt or stud. Example for
the use of various pipe fittings in pipe line is given in Figure 9.2
69
Figure 1: Various pipe joints.
70
Figure 2: Application of various joints in the pipe fittings
Valves and Meters
Valves are used in piping systems to control or stop the flow of liquid or gas. The most common types
of valves used in low pressure water pipe line are:
1.
2.
3.
4.
5.
6.
7.
Water tap
Water cock
Globe valve
Gate valve
Ball valve
Non-return valve
Foot valve
Water tap
To collect water from low pressure pipe line, water tap (screwdown valve) is commonly used. Figure gives the cross section of
the tap. Its leather or rubber faced valve disc is lifted or lowered
by rotating the spindle. Brass or gun-metal is the material used
for the valve body and the size is specified by the pipe to which
it is fitted, usually ranging from 10 mm to 25 mm.
Water cock
This is the simplest and smallest form of a valve in which a
conical plug called cock is inserted into a conical hole having a matching taper. A rectangular hole is
provided at the centre across the conical potion so that, in one position it permits flow of water as shown
in Figure. A half turn of the handle will bring the solid portion of
the cock to the water ways preventing the flow. Cocks are used for
low rate of water flow' or for tapping pressure line to a manometer
etc.
Globe valve
Globe valves are used as control valves in fluid (gas and liquid)
pipe lines. Figure shows the simplest and smallest type of globe
valve used in water pipe lines. Basically, the valve is a variable
opening flow device. The design of a globe valve also creates a
slight retardation to the flow because the fluid is forced to make a
double turn and passes through the opening at 90° to the axis of the pipe. The valve plug is raised or
lowered to stop or regulate the flow through a circular opening. A globe valve can be identified by the
71
spherical body and the arrow mark for the direction of flow. These valves are used in water pipe lines
from 12 mm to 100 mm or even larger diameter for the flow control purpose.
Gate valve:A gate valve is on-off type valve. It allows a straight-line movement of fluid and offer very
little resistance to the flow in fully opened position. The central disc moves completely out of the
passage and leaves a full opening. Figure shows a simple type of gate valve partially opened in position.
These valves are very widely used in water pipe lines of diameter
ranging from 12 mm to higher values. A gate valve can be identified
by its slim body. It is to be noted that there will be no arrow mark or
the body of valve because it can be used in both ways
Foot valve: Foot valve is a kind of non-return valve used in
centrifugal pumps. It is fitted at the bottom most end of the suction
pipe (Foot) to stop flow in the downward direction for priming
purpose. The strainer restricts the entry of floating materials to the
pipe line. Figure gives the details of the foot valve. The material used
may be cast iron, brass, or PVC.
72
POWER TOOLS
INTRODUCTION:
Power tool is a powered by an electric motor, a compressed air motor, or a gasoline engine.
Power tools are classified as either stationary or portable, where portable means handheld. They are
used in industry, in construction, and around the house for cutting, shapping, drilling, sanding, painting,
grinding, and polishing.
Stationary power tools for metalworking are usually called Machine tools.
The lathe is the oldest power tool, being known to the ancient Egyptians. Early industrial
revolution-era factories had batteries of power tools driven by belts from overhead shafts. The prime
power source was a water wheel or a steam engine.
Stationary power tools are prized not only for their speed, but for their accuracy. A table saw
not only cuts faster than a hand saw, but the cuts are smoother, straighter and more square than even the
most skilled man can co with a handsaw. Lathes produce truly round objects that cannot be made in any
other way.
An electric motor is the universal choice to power stationary tools. Portable electric tools may
be either corded or battery-powered.
Common power tools include the drill, various types of saws, the router, the electric sander, and
the lathe.
The term power tool is also used in a more general sense, meaning a technique for greatly
simplifying a complex or difficult task.
1. POWER HACKSAW:
A power hacksaw is a type of hacksaw that is powered either by its own electric motor (also
known as electric hacksaw) or connected to a stationary engine. Most power hacksaw are stationary
machines but some portable models do exist. Stationary models usually have a mechanism to lift up the
saw blade on the return stroke and some have a coolant pump to prevent the saw blade from
overheating.
While stationary electric hacksaw are reasonably uncommon they are still produced but saws
powered by a stationary engines have gone out of fashion. The reason for using one is that they provide
a cleaner cut than an angle grinder or other types of saw.
Fig. Power Hacksaw
Hand-Held circular saws:
73
The term circular saw is most commonly used to refer to a hand-held electric circular saw
designed for cutting wood, which may be used less optimally for cutting other materials with the
exchange of specific blades. Circular saws can be either left or right handed, depending on the side of
the blade where the motor sits and which hand the operator uses when holding a saw.
Fig. Circular saw (Portable)
5. DRILL:
A drill is a tool with a rotating drill bit used for drilling holes in various materials. Drills are
commonly used in woodworking, metalworking. Special designed drills are also used in medical and
other applications such as in space missions.
The drill bit is gripped by a chuck at one end of the drill and rotated while pressed against the
target material. The tip of the drill bit does the work of cutting into the target material, either slicing off
thin shavings (twist drills or auger bits), grinding of small particles (oil drilling), or crushing and
removing pieces of the work piece (masonry drill).
8. BENCH GRINDER:
A bench grinder or pedestal grinder is a machine used to drive an abrasive wheel (or wheels).
Depending on the grade of the grinding wheel it may be used for sharpening cutting tools such
as lathe tools or drill bits. Alternatively it may be used to roughly shape metal prior to welding or
fitting.
A wire brush wheel or buffing wheel can be interchanged with the grinding wheels in order to
clean or polish work-pieces.
74

engineering workshop lab manual

Transcription

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